“Ringing Out a Room”:

The process of identifying and compensating for problem frequencies within a room for the purpose of optimizing live audio within that space. This is typically done by sending pink noise through the speakers, turning up the microphones to the point of feedback, and using EQ to notch out the offending frequencies.

A/B Technique:

See “Spaced Pair.”


Abbreviation of Analog-to-Digital Conversion, the conversion of a quantity that has continuous changes (like electrical signals) into numbers that approximate those changes (i.e., computer data).

Absolute Phase:

This term describes a perfect polarity between an original signal (into the microphone) and the reproduced signal (through the speaker). When positive pressure exerted upon the microphone is translated as positive pressure to the loudspeaker, the two are in “absolute phase.”



In acoustics, absorption is what happens when sound waves are absorbed by a surface, as opposed to bouncing off the surface (reflection). Absorptive materials in a control room, for example, tend to “deaden” the sound of the room because the sound energy is absorbed rather than reflected. (See also “Reflection.”)


See “Alternating Current.”


A device that measures the acceleration to which it is subjected and creates an electric signal to match it. In music and audio, accelerometers are found in such things as microphones and guitar pickups.

Acorn Tube:

Named for its acorn-like shape, an acorn tube is a small vacuum tube used in ultra high frequency (UHF) electronics such as tube amplifiers.

Acoustic Amplifier:

The part of a musical instrument that vibrates in response to the initial vibration of the instrument, causing the surrounding air to move more efficiently and making the sound louder. For example: the body of an acoustic guitar, the bell of a horn, a drum’s shell, and the wooden soundboard of a piano.

Acoustic Echo Chamber:

A room designed with hard, non-parallel surfaces to create reverberation. In recording studios, they are used to add natural reverb to a dry signal.


The science of the sound—more specifically, the science of the properties and behavior of sound waves. A good understanding of acoustics is essential to audio engineering and studio design.

Active Device:

A component that is designed with the ability to control electrical current (as opposed to a “Passive Device”). In the recording studio, active devices are generally components that include an amplifier. (See also “Passive Device.”)


The part of a switch that causes change of the contact connections (e.g., toggle, pushbutton, or rocker).

Additive Synthesis:

A method of sound synthesis in which sounds are designed or created by combining simple waveforms together to create richer or harmonically diverse sounds.


Abbreviation for Attack, Decay, Sustain and Release, the four stages of volume changes in a sound event. ADSR controls are particularly useful on synthesizer instruments.


Audio Engineering Society.


Advanced Encryption Standard used by the U.S. government.


(sometimes called AES/EBU) A digital audio transfer standard developed by the Audio Engineering Society and the European Broadcasting Union for carrying dual-channel digital audio data between devices. AES3 is the protocol behind XLR cables, as well as RCA and S/PDIF cables.


(Also called “Pressure Sensitivity“) A feature in some keyboard instruments by which applying additional pressure to a key after it has been pressed can activate an additional MIDI control command. a synthesizer or Keyboard Controller of After Touch (a control or operational function of a synthesizer where pressing a key after it has been pressed, and before it is released, will activate a control command that can be set by the player).


A type of digital signal distortion that occurs in a sampler when the incoming signal frequency exceeds the Nyquist frequency for that unit. The sampler reproduces it at an incorrect frequency, or an “alias,” causing a distortion or artifact in the sound.  (See also “Nyquist Frequency.”)

Alternating Current (or AC):

The type of electrical current found in standard electrical outlets and studio signals running through audio lines. In AC, the current “alternates” directions, flowing back and forth through the circuit.



In most cases, this refers to the “atmosphere” of a certain place, like a restaurant. But in recording, it refers to the part of the sound that comes from the surrounding environment rather than directly from the sound source. For example, the sound waves coming into your ears from a cello being played are coming directly from the source, but the sound of the same cello coming to you after bouncing off the back wall is ambient sound.

Ambient Field:

The area away from the sound source where the reverberation is louder than the direct sound.

Ambient Miking:

This refers to placing a microphone in the ambient field of a room to record the ambient reverberations of the sound.  The recording engineer often does this in addition to direct micing of the instrument(s) to create a blend or mix of direct and reverberant sound in the recording.


An abbreviation for “Amplifier,” “Amplitude” or “Ampere,” depending on context. (See below.)


The unit of measure for electrical current, abbreviated Amp.


A device that increases the level or amplitude of an electrical signal, making the resulting sound louder.


The height of a waveform above or below the zero line. In audio, this usually translates to the signal strength or the volume of the sound.


A continuously changing representation of a continuously variable quantity. In the context of audio, this refers to using continuously changing electrical signals (voltage) to represent the continuously variable frequencies of sound, and/or recording those signals to an analog medium. Analog is in contrast to digital, which represents constantly changing quantities in the form of fixed numeric values.

Analog Recording:

A recording of the continuous changes of an audio waveform. The most common example of analog recording in a recording studio is recording on reel-to-reel magnetic tape.


Analog To Digital Converter (A/D):

A device that translates a continuously changing signal (analog) into numeric values that approximate those changes (digital). In audio recording, this refers to converting recorded sound from electrical voltages to computerized data.


The initiation of a sound. In terms of the four stages of a sound (Attack, Decay, Sustain and Release, or ADSR), a sound’s attack is the point where the sound begins and increases in volume to its peak.



The reduction of electrical or acoustic signal strength. In audio, attenuation is measured in decibels (dB) and is typically heard as a reduction in volume. Sound waves traveling through the air naturally attenuate as they travel away from the source of the sound. Engineers also purposefully attenuate signals in the studio through gain controls or pads to prevent overload.


In its broadest sense, audio is the range of frequencies we humans can hear with our ears. In the technical sense, audio refers to the transmission, recording or reproduction of sound, whether digitally, electrically or acoustically.


Automatic Dialogue Replacement (ADR):

The process of re-recording dialogue for film in a controlled environment after the film is shot, for the purpose of replacing poorly recorded dialogue.


Automatic Gain Control:

A compressor with a long release time, which is used to keep the volume of the audio at a consistent level.



Programming certain changes to occur automatically during recording and/or playback. In the studio, engineers use automation on their consoles or computers so various parameters will change automatically at different times during multitrack recording and playback. This pre-programming feature makes it easier to create those changes than attempting to perform them all manually in real time.

Auxiliary Equipment:

External signal processing devices that work alongside the mixing console to modify the signal.

Auxiliary Return:

(Abbreviated Aux Return or Return) The input on a console or DAW that returns the effected signal sent through the auxiliary send back into the channel mix.


Auxiliary Send:

(Abbreviated Aux Send or Send) A control to adjust the signal level being sent from the input channel on a console or DAW to auxiliary equipment or plug-ins through the auxiliary bus. This is typically used for creating an effects loop that processes a portion of the signal, then returns it into the mix through the auxiliary return.


An imaginary line around which a device operates. For example: in microphone use, the axis is an imaginary line coming out from the front of the microphone in the direction of motion of the diaphragm, delineating the optimum location for the mic to pick up the sound. Sounds that occur “off-axis” from the microphone will not be picked up as clearly.

Background Noise:

Refers to either 1) The ambient noise in a room unrelated to the instrument(s) or vocal(s) being recorded; or 2) The system noise unrelated to the recorded signal. (All electronics emit a level of noise.)


Sound absorbing panels that are used to prevent sound waves from entering or leaving a space.


1) The relative level of two or more instruments in a mix, or the relative level of audio signals in the channels of a stereo recording. 2) To even out the relative levels of audio signals in the channels of stereo recording.



Balanced Cable:

A cable consisting of three wires (two signal wires and a ground wire) and two connectors. The two signal wires carry the same signal in opposite polarities, providing protection against interference and noise in a balanced system. Examples of balanced cables include tip-ring-sleeve (TRS) stereo cables and XLR cables.

Balanced Mixer:

A circuit or device that generates the sum and difference frequencies of two input signals.


1) A range of frequencies, often identified by the center frequency of the range. 2) A group of musicians playing together.

Band Pass Filter:

A device, circuit or plug-in that allows a narrow band of frequencies to pass through the circuit, rejecting or attenuating frequencies that are either higher or lower than the specified range.


Band Stop Filter:

A device, circuit or plug-in that attenuates a narrow band of frequencies in the signal, allowing frequencies outside the band to pass. The exact opposite of a band pass filter.

Band Track:

(Sometimes abbreviated “Track“) A mixdown of a song minus the lead vocal and/or background vocals. In other words, a mixed track containing only the instrumental parts of the song.



In signal processing, bandwidth refers to the usable frequency range of a communication channel, measured by the difference between the device’s highest and lowest usable frequencies.



1) A collection of sound patches, sequencer data and/or operating parameters of a synthesizer’s generators and modifiers in memory.  2) A group of sound modules as a unit.


In music notation, bar is another term for measure—a specified period of time containing a certain number of beats, and marked by bar lines on each side of the written measure.


Barrier Miking:

A microphone placement technique in which a microphone is placed close to a reflective surface. When done correctly, barrier miking ensures that both the direct and reflected sounds reach the microphone simultaneously, preventing phase cancellation between the two.

Basic Session:

The first audio recording session for recording the basic tracks that serve as the song’s foundation (for example, the drums and bass).


The lower range of audio frequencies up to approximately 250 Hz. A reference value.


Bass Reflex:

A type of loudspeaker cabinet design in which a port (opening) in the speaker cabinet enhances bass frequencies. The principle is that the sound pressure generated by the back of the speaker cone inside the cabinet is routed out the port at the front of the cabinet, mixed with the sound coming from the front of the woofer. Changing the port size and position will greatly change the character of the low frequencies.


A phenomenon found in loudspeakers in which higher frequencies are projected straight out of the loudspeaker, rather than dispersing along with the lower frequencies. When you stand on-axis in front of the speaker, it sounds as though it is only reproducing the high frequencies, rather than the mids or lows. This phenomenon is alleviated by routing the high frequncies through horns in the loudspeaker.


1) The steady, even pulse in music. 2) The action of two sounds or audio signals of slightly different frequency interfering with one another and causing periodic increases and decreases in volume, heard to the ear as “beats.”


Beat Mapping:

The process of adjusting the tempo variations in a recorded piece of music to fit the set tempo of the project. In a DAW, this is done using time stretching tools and cuts to synchronize the transients to the appropriate tempo markers. This technique is often used, for example, to reconcile a drum or bass performance that was recorded without a click track.


A technique predominantly used by DJs to synchronize the tempos of two recorded tracks, generally through the use of time stretching and pitch shifting tools, to create a seamless transition from one song into another.


Beats Per Minute (B.P.M.):

The number of steady even pulses in music occurring in one minute, defining the tempo of the song.



A technique in which high and low frequencies in a speaker or speaker system are driven by two separate amplifiers.

Bi-Directional Pattern:

A microphone pickup pattern which is most sensitive to picking up sounds directly in front and back of the mic, effectively rejecting sounds coming from the sides. Also called a “figure-8 pattern.”



A numbering system in which all numeric values are described by occurrences of the symbols “0” and “1.” Most digital data is expressed in binary.


The smallest unit of digital information representing a single “0” or “1.”

Bitrate (or Bit Depth):

In digital recording, the number of computer bits used to describe each sample. The greater the bitrate, the greater the dynamic range of the sampled sound. The quality and resolution of an audio sample are described as a combination of sample rate and bitrate. (See also “Sample Rate.”)



The mixing of multiple sounds or channels together to form one sound, or mixing the left and right signals together.


A telescoping support arm attached to a microphone stand holding the microphone.


Boom Stand:

A microphone stand equipped with a telescoping support arm to hold the microphone.


To increase gain at specific frequencies with an equalizer.


(also called “Ping-Ponging” or “Ponging“) The technique of combining and mixing multiple tracks onto one or two tracks (mono or stereo). This can be done in real-time or analog by playing the tracks through the console and recording them onto separate tracks, or digitally through a digital audio workstation. Bouncing was once used frequently by engineers to free up additional tracks for recording, but in digital workstations where tracks are virtually unlimited, this practice is basically obsolete. Today, engineers typically bounce tracks for the purpose of creating a preliminary or final mix of a song.


Boundary Microphone:

An omnidirectional microphone designed to be placed flush against a flat surface (or boundary), effectively creating a “half-Omni” pickup pattern while eliminating the danger of phase issues from reflected sounds. A popular type of boundary microphone is Crown Audio’s trademark Pressure Zone Microphone (PZM).



An abbreviation of Beats Per Minute, the number of steady even pulses in music occurring in one minute which defines the tempo.


See “Pumping and Breathing.”

Brickwall Filter:

A certain type of low-pass filter exhibiting a steep cutoff slope which resembles a “brick wall.” While these filters are often found in A/D converters to prevent aliasing, their steep cutoff can introduce unwanted side-effects to the audio signal, such as phase shift.


A technique of feeding a single input to both channels of an amplifier, then summing them into one, thereby effectively doubling the amplifier power supplied to the signal.


A type of phase cancellation in which two identical signals or frequencies, having the same amplitude but opposite polarity, cancel one another out. Most commonly used in the context of musical instrument frequencies. EXAMPLE: a “Humbucker” guitar pickup is designed to remove or “buck” hum frequencies from the signal using this principle.

Bulk Dump:

Short for System Exclusive Bulk Dump, a method of transmitting data such as the internal parameters between MIDI devices.


An audio pathway by which one or more signals, usually from different sources, are routed to a designated place. Because busses are highly connected to signal flow, they serve a broad range of purposes in audio applications. 2) A shorthand term for the signals themselves that are routed through the bus (see also “Subgroup”).


Information (data) bits in a grouping of eight. One byte = eight bits.


A group of one or more insulated conductors, optical fibers, or a combination of both within an enveloping jacket, typically for transmitting electrical signals of different types.


Cable Assembly:

Cable that is ready for installation in specific applications and usually terminated with connectors.

Cable Harness:

A grouping of cables or wires used to interconnect electronic systems.

Cable Sheath:

Conductive protective cover that is applied to cables.


An electronic device made of two plates separated by an insulator, designed to store electrostatic energy. The capacitor is a key component in condenser microphones, for example.



A mechanical part of a magnetic tape recorder that controls the speed of the tape as it passes across the tape heads.


Space-travel definitions aside, this is the name given to the part of a microphone that contains the diaphragm and active element, the mechanical structure that converts acoustic sound waves into electrical current.

Carbon Microphone:

A microphone that uses carbon granules to convert sound waves to electrical impulses. The carbon element sits between two plates; as sound waves hit the carbon granules, it generates changes in resistance between the plates, affecting the electrical signal.

Cardioid Pattern:

A microphone pickup pattern which is most sensitive to sound coming from the front, less from the sides, and least from the back of the diaphragm. So named because the pickup pattern is in the shape of a heart (cardio).



To connect or “daisy chain” two mixers so that the stereo mixing busses of the first mixer feed into the stereo busses of the second.


An abbreviation for Compact Disc, or a small optical disk with digital audio recorded on it.


Center Frequency:

The frequency of an audio signal that is most affected by an equalizer, either boosting or attenuating the frequency. Drawn graphically, this is the very top or bottom (the “peak”) of the frequency bell-shaped curve.



1) An audio recording made on a portion of the width of a multitrack tape, or isolated within a digital audio workstation, usually for the purpose of combining with other channels. 2) A single path that an audio signal travels or can travel through a device from an input to an output.


Channel Path:

The complete signal path from the sound source to the multitrack recorder (or DAW). For example, an audio signal that travels from the microphone to the preamplifier, then into a channel strip on the mixing console, then is sent through the outputs into the recorder. This is different from the monitor path, which feeds a mix of signals into monitor speakers or headphones without affecting the recorded signals. (See also “Monitor Path.”)



The automatic adjusting of the speed of a recorder (or sequencer) to keep time with another recorder.



Three or more musical pitches sung or played together.


Chord Chart:

A shorthand form of musical notation that provides the basic chord changes and essential rhythmic information of a song. Most commonly used by studio session players, rhythm sections or jazz bands to provide the skeletal structure of the song while allowing players room to create their own parts and improvise. While lead sheets typically focus on melody line and chord structure, chord charts display mainly chord changes and rhythm. (See also “Lead Sheet.”)



1) The part of a song that is repeated with the same music and lyrics each time, often containing the main point or hook of the song. 2) A musical singing group with many singers. 3) A delay effect that simulates a vocal chorus by adding several delays with a mild amount of feedback and a medium amount of depth.



1) One complete path of electric current. 2) Similar to definition 1, but including all audio signal paths and components to accomplish a particular audio function.

Click Track:

A metronome “click” fed into headphone monitors for the purpose of helping the musicians play in time with the song.


The distortion of a signal due to overloading an electronic device, so named because the resulting graphic waveform looks like the edges of the waveform have been “clipped.”


Clock Signal:

A signal sent by a device within the circuit that generates steady pulses or codes to keep other devices in sync with each other. An example in the music world is sequencing via MIDI. The sequencer sends a clock signal so connected devices will play in time.


Close Miking:

A microphone placement technique that places the mic close to the sound source to pick up the direct sound and reject ambient sound.

Coaxial Cable:

(abbreviated “Coax”) A two-conductor cable that consists of one conductor surrounded by a shield.


Coincident Miking:

A stereo miking technique in which two microphones are placed with their heads as close to each other as possible. This prevents phase cancellation problems in the mix because the distance from the sound to either microphone is the same.


A signal processor serving as a combination compressor and expander, primarily used for noise reduction purposes in analog systems.  The audio signal is compressed prior to recording, then expanded at the reproduction stage. Companding is the principle behind Dolby noise reduction systems.



1) In digital audio workstations (DAWs), the process of blending portions of multiple recorded takes to create a “compliation” track. (See also “Take,” “Playlist.)  2) In jazz music performance, an abbreviation for “accompanying.”



1) In signal processing, the action performed by a compressor (see also “Compressor”). 2) In acoustics, the increased air pressure caused by the peak of a sound pressure wave, used in the context of “compression and rarefaction” (see also “Rarefaction”).

Compression Driver:

A diaphragm that feeds a sound pressure wave into a horn loudspeaker.

Compression Ratio:

The rate by which a compressor attenuates an incoming signal, measured in decibels. For example, a compression ratio of 4:1 means the compressor will only allow a 1 dB increase in the signal for every 4 dB increase in the signal above the threshold.



A signal processor or plug-in that reduces the dynamic range of an audio signal by amplifying its quieter sections and attenuating its louder ones.


Condenser Microphone:

A microphone in which sound is converted into electrical current through changes in a capacitor. The sound pressure waves move the diaphragm, producing changes in capacitance which are then changed into electrical voltage.



See “Mixing Console.”

Contact Microphone:

A microphone designed to pick up vibrations from solid objects (as opposed to vibrations in the air). Also known as a “pickup” or “piezo,” this microphone is often used as an acoustic guitar pickup to pick up the vibrations from the soundboard, or by experimental musicians creating “noise music” from a variety of objects.



In the broadest sense, a controller is any device that is used to control another device. Most commonly used in the context of MIDI controllers, which send out MIDI signals to control other connected MIDI instruments and devices. Other examples of controllers in the recording studio can include monitor controllers, DAW controllers and DJ controllers.

Corner Frequency:

See “Cutoff Frequency.”


Abbreviation for Central Processing Unit, the main “brain” chip in a computer (also known simply as “Processor”).


Critical Distance:

The distance from the sound source at which the direct sound and the reverberant sound are at equal volume. Critical distance varies according to the space; in a room with absorbent walls, the critical distance will be further from the source, and in a reverberant room, the distance will be closer to the source.


An audio editing technique in which one sound is faded out as another sound is faded in, to create a seamless transition between the two. Audio engineers use crossfading, for example, to blend two takes or more “takes” of a recorded track into a composite take. Club DJs also use crossfading to transition from one song to the next with no stops.



An audio filter component that splits an audio signal into two or more bands or signals, usually to be fed into different components of a loudspeaker system according to frequency range. (Also called a “crossover network.”)

Crossover Frequency:

The frequency at which the crossover stops sending the signal to one speaker and starts sending it to another.


The unwanted leakage of an audio signal between two audio channels—for example, overlapping signals between channels on a mixing console, or overlapping audio between two tracks of audiotape.


In general terms, a cue is the starting point for a piece of music or section of music. Depending on the context, the word “cue” may describe: 1) The point at which a musician or vocalist is supposed to start playing or singing; 2) The audio fed to the musicians through headphones so they can determine when to start playing/singing; 3) A specific location point on the music timeline within a DAW or on the tape; or 4) To set the tape or disc to a certain starting point in the song (“cueing” the tape). A cue can even refer to an entire section of music being used for video production. (Confusing, huh?)

Cutoff Frequency:

The frequency in a filter beyond which other frequencies are attenuated.

Cutoff Slope:

The rate of reduction of the frequencies beyond the passband of a filter. The slope is described as the number of dB the filter reduces the signal for each octave past the cutoff frequency.



One complete expression of a waveform beginning at a certain point, progressing through the zero line to the wave’s highest and lowest points, and returning to the same value as the starting point. One complete vibration or sound wave.


D-Sub Connector:

Abbreviation for “D-subminiature connector,” a D-sub is a multipin connector that is most often used to connect a computer to a VGA monitor, but also used occasionally in digital audio applications in the recording studio.



Abbreviation for Digital to Analog conversion, which changes digital data numbers (digital audio signal) into discrete voltage level. The reverse process of A/D.


Daisy Chain:

The connection of three or more devices in a series, where the audio signal passes through one device to reach a second, and through the second to reach the third, etc.


The reduction of energy in a vibrating system, through friction. Can refer to the reduced amplitude in an electrical signal, or the stifled vibrations of a musical instrument (for example, the damper pedal on an acoustic piano).

Damping Factor:

Describes an amplifier’s ability to restrain the pushback motion (back-EMF) of the loudspeaker cone when the audio signal stops.


An abbreviation for Digital Audio Workstation, a device or software program designed for recording and mixing audio digitally.


An abbreviation for decibel, a measurement ratio that compares signal strengths (usually audio levels).


A series of noise reduction systems, named for the company that developed them. DBX noise reduction has been less commercially successful than the more widely known Dolby systems, but is still found on occasion in recording studios.



see “Direct Current.”


An audio compressor designed to reduce the volume of sibilant sounds and frequencies, especially those produced by pronouncing the letter “s.”


The second stage of the four stages of a sound (Attack, Decay, Sustain and Release, or ADSR), the decay of the sound is its gradual reduction in volume after reaching its peak in the attack stage.


Decca Tree:

A stereo microphone placement technique involving three microphones (usually omnidirectional) placed in a “T” pattern. Commonly used in miking choirs, orchestras and other large ensembles, but variations of the Decca tree technique are also being used today in surround sound situations.


(abbreviated “dB“) The ratio measurement of two levels according to a scale where a certain percentage change comprises one unit. Most often used to describe audio levels.


The process of demagnetizing an object. In the context of audio, degaussing essentially erases the recording on magnetic tape.


1) An process by which an audio signal is recorded to a medium or device, reproduced at a time delay, then mixed with the original, non-delayed signal to create a variety of effects such as a fuller sound, echo, chorusing, flanging, etc.  2) A signal processor that creates delay effects.


A preliminary recording that is intended to give the listener an idea of how a song could sound in a final production. A demo usually involves minimal tracking or production, almost like a “rough draft” of a recording.


To purposely cause an instrument or signal to play out of tune (usually slightly). This effect can be used for a number of purposes in the studio, but is often used in “double-tracking,” blending the detuned instrument/track with the original to create a fuller sound.


see “Direct Injection.”


The spoken word recorded in film/video sound, commercials and instructional recordings.


The part of a microphone that moves in response to sound waves, converting them to electrical signals.

Digital Audio Workstation:

(abbreviated DAW) A device or computer software that records and mixes audio digitally and creates digital audio files. A DAW can be a standalone unit or an integrated set of components, but today they are most commonly found as “in-the-box” software programs run from a computer. The most common DAW program found in recording studios is Pro Tools; other commonly used programs include Reason, Ableton and Logic.


Digital Multimeter:

see “Multimeter.”

Digital Recording:

The process of converting audio signals into numbers that represent the waveform, then storing these numbers as data.


Digital Signal Processing:

(abbreviated “DSP”) Any signal processing done after an analog audio signal has been converted into digital audio.

Digital to Analog Converter:

(abbreviated D/A) A device that converts the digital data of digital audio into voltage levels that approximate the original analog audio.

DIN Stereo:

A stereo microphone placement technique that places two cardioid microphones about 20cm apart and set outward from each other at a 90-degree angle to create a stereo image.  Particularly for stereo miking at close ranges. (See also “Near-Coincident Miking.”)


An electrical component that enables easy electrical current flow in one direction but not the other. In the recording studio, these are commonly found in the vacuum tubes of tube amplifiers.

Direct Box:

A small device that to converts an unbalanced, high-impedance speaker or instrument-level output to a balanced, low-impedance mic-level output. Frequently used in the signal path connecting electric instruments “directly” to the mixing console, as opposed to miking them acoustically. Also called “direct injection box” or “DI box.”

Direct Current:

(abbreviated “DC“) Electrical current that flows in a single direction, as opposed to Alternating Current (AC), which flows in alternating directions. Many electronic devices run on DC, which is usually provided by battery power, USB power or an AC adapter plugged into the wall.

Direct Injection:

(abbreviated “DI”) The process of sending an electrical audio signal directly from an instrument to the mixing console through the use of electric pickups or direct boxes, as opposed to using a microphone.

Direct Out:

An output available on some consoles which is fed directly from the preamplifier stage of the input, bypassing the channel strips and faders. This feature is often used to send a “dry” signal to a monitor mix or a recording device.

Direct Sound:

The sound that reaches a microphone or a listener’s ear without hitting or bouncing off any obstacles (as opposed to reflected or ambient sound).

Directional Pattern:

1) In microphones, a term meaning the same thing as “Pick Up Pattern,” a description of the area in which a microphone is most sensitive to sounds. 2) In loudspeakers, it is the pattern of dispersion, the area that the sound from a speaker will evenly cover in a listening area.

Dispersion (also Dispersion Angle):

The area that is effectively covered by the sound coming from a loudspeaker; specifically, the imaginary boundaries on either side of the speaker at which the sound level is 6 dB lower than if you were standing directly in front of the speaker. Each speaker has both a horizontal and vertical dispersion angle.


Distant Miking:

The technique of placing a microphone far from the sound source in order to pick up a combination of the direct and reflected sounds.


Refers to the deforming of a waveform at the output of a device as compared with the input, usually due to overload, creating a distorted or “dirty” signal. While electrical or audio distortion is typically unwanted and avoided, it is frequently used in controlled situations in audio to create certain desirable effects, particularly with electric guitars and amplifiers.


1) In audio settings: the use of two or more antennas in a wireless receiver system to prevent dropouts in the audio from a wireless microphone. 2) In other settings: the embracing of the uniqueness of all individuals.


The brand name of a manufacturer of noise reduction systems and other audio systems, to improve performance and fidelity of audio recording, playback, and transmission.

Doppler Effect:

The phenomenon in which the human ear perceives a change in the frequency (pitch) of a sound while the sound source is in motion. As the sound source approaches, the sound waves travel a shorter distance to the ear, increasing the frequency of the waves and the pitch of the sound; as the sound source moves away, the sound waves must travel farther and farther, resulting in lower frequencies. A common example of this effect is an approaching emergency vehicle whose siren sounds higher as it approaches and lower after it passes. The Doppler Effect can be utilized in audio settings, for example, in the  Leslie speaker in which an electric motor rotates the speakers inside the cabinet, constantly changing the distance between the sound source and the listener (or microphone) and creating its signature warbling vibrato effect.


1) To record a second performance closely matching the first performance, for the purpose of blending the two tracks. 2) To use a delay line with medium delay to simulate double tracking.



1) A transducer in a loudspeaker that converts electrical signals into sound pressure waves. 2) A computer program that controls an attached device or piece of hardware.



A brief loss of audio signal on tape, or a brief loss of data in a digital audio file (often due to a dropped sample), that can result in an unwanted dip in audio, a crackle or a pop.

Drum Machine:

An electronic device containing synthesized and/or sampled drum sounds in its memory, along with an internal sequencer that can be programmed to play drum patterns or loops.

Drum Pattern:

A specific sequence of drum sounds played by a drummer or sequenced into a drum machine for use in a song.


Describes a sound that has no reverberation or ambience, or an audio without any signal processing, as opposed to “wet.” In mixing, many engineers prefer a blend of wet and dry versions of a signal. (See also “Wet.”)


see “Digital Signal Processing.”

Dub (or Dubbing):

1) To copy a recording. 2) To record in real time with another recording with the intent of mixing the two recordings (see also “Overdub/Overdubbing”). 3) “Dub” is an abbreviation for “dubstep,” a style or subgenre of electronic music.


A compression-based audio effect in which an audio signal is reduced proportionately by the presence of another audio signal, sometimes accomplished through a “sidechain” connection with the signal processor. A notable example is a spoken-word voice-over track recorded over a musical track, where the music drops in volume when the speaker begins to speak. A more subtle example is when an audio engineer “ducks” specific sounds to make room for others in the track; for example, when a bass guitar signal triggers a slight reduction in the level of drums or guitars. (See also “Sidechain.”)

Dynamic Microphone:

(Also called Moving Coil Microphone) A microphone in which sound pressure waves are converted to an electrical audio signal by an induction coil moving within a magnetic field—a process often compared to a loudspeaker working in reverse. Dynamic microphones are less sensitive than condenser microphones, but can be effective for miking louder sound sources or for close-miking applications.

Dynamic Processing/Dynamic Signal Processing:

The process of automatically changing the level (or gain) to alter the level relationship of the loudest audio to the softest audio. Dynamic processors include compressors, limiters, expanders and gates.

Dynamic Range:

1) The ratio (in dB) between the loudest peak and the softest level of a song or recording. 2) The ratio (in dB) between the softest and loudest possible levels a device or system can provide without distortion.

Early Reflections:

The first sound waves that reach a listener’s ear after bouncing off a surface in the room, usually heard almost immediately after the initial sound. The first stage of reverberation.


The distinct repetition of an initial sound, caused by the reflection of the sound waves upon a surface. We recognize a sound as an echo when the distance between the source and the reflection is far enough apart that we can detect the time delay between one and the other. Essentially, reverberation is the combination of many echoes occurring too rapidly to hear each individually. In the studio, echoes can be reproduced acoustically or simulated by a digital signal processor.

Echo Chamber:

An enclosed room designed with reflective, non-parallel surfaces for the purpose of creating acoustic echoes (reverberation).


To change one or more parameters of a recorded sound after the fact. This can take many forms, including “punching in” a section of the music that is re-recorded to replace the original version; altering the shape/size of waveforms graphically; changing the sequence of playback; and many others. Analog editing would typically involve splicing the magnetic tape on which the audio signals were recorded. These days, almost all editing in the studio is done via computer using a digital audio workstation (DAW).


1) Various ways an audio signal can be modified by adding something to the signal to change the sound.

2) Short for the term Sound Effects (sounds other than dialogue, narration or music like door closings, wind, etc.) added to film or video.

Effects Processor:

(Also called Guitar Processor) A device that adds audio effects to a direct guitar signal, such as reverb, chorusing, flanging, delay, overdrive, amplifier simulation, etc. Effects processors can occur as individual effects boxes or multi-sound pedal boards (see also “Foot Pedals,” “Foot Switches”) added into the signal path between the guitar and the console. They can also be found as presets in guitar amplifiers, or even as digital plug-ins within a DAW.

Effects Track:

1) In film production audio, a recording of the mixdown of all the sound effects ready to be mixed with the dialogue and music.

2) In music recording, one track with a recording of effects to be added to another track of a multitrack recording.


A dielectric plate that is designed with permanent polarity, allowing it to function similarly to a magnet. (“Electret” comes from the words “electricity” and “magnet.”) Used in some microphone types in place of a capacitor (condenser).

Electret Microphone:

A variation of condenser microphone that uses an electret instead of a capacitor. (Also called “Electret Condenser Microphone.”) Because the electret is permanently polarized, an electret microphone does not require an external power source as a standard condenser microphone does.

Electromagnetic Field:

(Abbreviated EMF) A field of magnetic energy put out because of current traveling through a conductor.

Electromagnetic Interference (EMI):

The bane of audio professionals everywhere, EMI is a type of interference caused by nearby electromagnetic activity, which can be picked up by audio cables and equipment, causing unwanted noise, hum or buzz in audio systems. Common causes of EMI in audio systems may include high-current power lines, fluorescent lighting, dimmer switches, computers, video monitors and radio transmitters.


Negatively charged particles revolving around the nucleus of an atom. Electrical current is generated by electrons moving along a conductor, like a metallic wire.


The collective term for the four elements of the lifespan of a sound: Attack, Decay, Sustain and Release (ASDR). The envelope of a sound describes how a sound or audio signal varies in intensity over a period of time.

Equal Loudness Contours:

A drawing of several curves showing how loud the tones of different frequencies would have to be played for a person to say they were of equal loudness. (See also “Fletcher-Munson Curves.”)


An audio signal processor that uses one or more filters to boost or cut the amplitude (volume) of certain frequencies within the sound. The underlying principle is to balance or “equalize” the frequency response of the audio system, or to create balance between multiple signals in a sonic space. However, audio engineers may use equalizers to alter or “color” the sound in many different ways.


A signal processor (or plug-in) that performs the opposite function of a compressor, expanding the dynamic range of an audio signal rather than compressing it. It accomplishes this by further reducing the amplitude of signals that drop below a set threshold.

Expansion Ratio:

The rate by which an expander attenuates an incoming signal, measured in decibels. For example, an expansion ratio of 2:1 means the expander will reduce the signal by 2dB for every 1dB it drops below the threshold. If the signal falls 3dB below the threshold, the expander attenuates it by 6 dB, and so on.


A gradual reduction of the level of the audio signal, or a gradual change of level from one pre-set level to another.


A control which adjusts the level (gain or attenuation) of an incoming signal to a channel or grouping of channels on a console.

Far Field:

The region away from a loudspeaker at which the sound drops 6dB for each doubling of the distance, up to the critical distance. The beginning of the far field varies according to the size of the speaker, but in most cases the far field begins around 3 feet from the sound source. Audio engineers often use both near field and far field monitoring when fine-tuning a mix. (See also “Critical Distance,” “Near Field.”)


To send an audio or control signal to.


The return of a portion of the output signal back into the input of a system. This can be done in a controlled manner through a feedback circuit to alter the sound of an instrument (most commonly electric guitars or analog synths). It can also describe the unwanted feedback loop created when an open microphone is picking up the sound from a nearby speaker, generating a loud, oscillating frequency that increases in intensity until the feedback loop is broken by turning off the mic or speaker, or by use of an equalizer to attenuate the frequency.

Feedback Control:

The control on a delay line or delay effects device that controls the amount of feedback into the system.

Figure-8 Pattern:

See “Bi-Directional Pattern.”


A device that removes or attenuates signals with frequencies above or below the specified cutoff frequency.


An audio effect caused by blending the signal with a copy of that signal at a slight time delay, then modifying the delayed copy, creating a “swirling” sound. This was originally accomplished in analog tape recording by playing the original tape and the copy on two tape machines simultaneously, then physically pressing on the flange of one of the machines to alter the timing of the duplicate track. These days, most flanging is done through delay boxes or digital plug-ins.


1) A term used to describe an even frequency response in a device or speaker, meaning that the device/speaker treats all frequencies the same without the need for EQ. When displayed graphically, the frequency response is shown as a “flat” line with no peaks or valleys.  2) In music, describes a note or pitch that is out of tune, sounding at a slightly lower frequency than it should. 3) In music notation, an “accidental” mark that instructs the player to play/sing the note one-half step lower.

Fletcher-Munson Curves:

Also known as “Equal Loudness Contours,” a set of graphical curves plotted to illustrate how the human ear responds to different frequencies at different volume levels. Named after the two researchers who first plotted the curves. (See also “Equal Loudness Contours.”)

Floating Unbalanced Line:

A connection “workaround” in which an unbalanced output is connected to a balanced input by modifying the connections in the line to resemble a balanced line, alleviating unwanted hum or buzz.

Fly In:

To add sounds into a mix or recording that have no synchronization.


See “Front-of-House.”


A stage monitoring system used in live audio. A set of on-stage speakers called monitors or wedges (or “foldback speakers” in British countries) are fed a special mix of audio signals for the onstage performers to hear in order to play. This mix is usually different from the FOH (front-of-house) mix that the audience hears, and is sometimes controlled by a second engineer through amplifiers and speakers separate from the main sound system. This type of stage monitoring is frequently susceptible to feedback from the microphones, and in certain venues can cause unwanted reflective noise that makes it difficult for FOH engineers to create a good mix for the audience. For this reason, many live audio systems now use in-ear monitoring as an alternative to stage monitors to control the onstage noise and reduce the risk of feedback.

Foot Pedal:

An effects device controlled by a musician with his foot.

Foot Switch:

A switch placed on the floor and pressed by a musician to do various functions.


An element in the sound of a voice or instrument that does not change frequency as different pitches are sounded. Formants are essentially “fixed” frequencies or resonances that occur as a result of the physical structure of the sound source. These frequencies are what create timbre, that element of sound that creates the specific sound of a guitar, a flute, a male or female voice, etc.


1) One of many different media used to store and reproduce audio, whether in the recording studio or for listening purposes. Examples include currently used physical formats such as vinyl records and compact discs; obsolete formats such as cassette tape, 8-track tape and DAT; analog recording staples such as reel-to-reel multitrack tape; and many different digital audio file formats such as mp3, WAV, WMA, AIFF and others. 2) Format can also describe specific parameters when recording to analog tape, such as number of tracks, width, spacing and order. 3) To prepare a hard drive or memory card for use, usually erasing all existing data in the process.


The number of occurrences of a particular event within a certain amount of time. In audio and acoustics, frequency specifically refers to the number of complete cycles a vibration or waveform makes in a second, measured in cycles per second, or Hertz (Hz). In sound, frequency determines what we hear as pitch. The longer the wavelength, the fewer the cycles per second, and the lower the pitch.

Frequency Modulation (FM) Synthesis:

A method of sound synthesis in which the frequencies generated by one oscillator (the carrier) are altered by the output of one or more additional oscillators (operators) to create a diversity of harmonically rich sounds.

Frequency Range:

1) The range of frequencies over which an electronic device puts out a useful signal (see also “Bandwidth”). 2) The range of frequencies that can be substantially transmitted or received in relation to a sound source. Each instrument has a certain frequency range in which it can play; the human ear can also hear within a certain frequency range.

Frequency Response:

The range between high and low frequencies that a component of an audio system can adequately handle, transmit or receive.


In wireless microphone systems, frequency-agile describes the ability of the system to operate on a choice of different RF frequencies within a certain bandwidth. Frequency-agile systems are preferred for live touring and in areas with high concentrations of radio signals (like large cities) because the RF frequency of the device can be changed to avoid interference.

Frequency-Shift Key (FSK):

A now out-of-date protocol in which a sync tone is recorded onto a spare track of a multi-track tape recorder to enable electronic devices (mainly drum machines) to perform in sync with the tape. While some older devices still read FSK, an updated protocol (Smart FSK) is now more commonly used. (See also “Smart FSK.”)


(Abbreviated FOH) In live audio settings, the location in a venue opposite the stage, where live audio for the show is controlled and mixed.


See “Normalled.”


(Also called fundamental frequency or first harmonic) The lowest frequency present in the sounding of a note by musical instrument or voice.


1) The amount of increase in audio signal strength, often expressed in dB.

Gain Control:

A device that changes the gain of an amplifier or circuit, often a knob (potentiometer) that can be turned. In a mixing console, each channel usually has its own gain control to regulate the gain of the signal coming into the board—not to be confused with the channel “fader,” which regulates the output of an already-amplified signal.

Gain Reduction:

The action of a compressor or limiter in regulating the amplitude of the audio signal.

Gain Structure:

A term that describes the interconnection of multiple components in an audio system, and the amount of gain increase or reduction that occurs at each point. A configuration with a good gain structure means that the components are working properly together to provide optimal gain with minimal distortion or noise.


(Also called Noise Gate) A type of expander that completely (or almost completely) attenuates a signal once it drops below a certain level, rather than simply reducing the level. (See also “Expander.”)


A term used to describe the number of times that the recorded audio signal has been copied.

Generation Loss:

The amount of clarity lost when recorded audio is copied, due to added noise and distortion.

Golden Section:

(also called Golden Ratio) A ratio of height to width to length, where the width is approximately 1.6 times the height, and the length approximately 2.6 times the height. First calculated by the ancient Greeks, this ratio (known mathematically as “phi”) is used as an optimal ratio in many applications, including room dimensions and studio design (to achieve “optimal acoustics” in the room), and even in the design of certain acoustic instruments.

Graphic EqualizerGraphic Equalizer:

A type of equalizer that can adjust various frequencies of the incoming signal using sliders that are assigned to specific frequency bands. (See also “Equalizer.”)

Ground Lift PlugGround Lift Plug:

An adapter that enables a three-prong power cord to plug into two-prong outlet. Some engineers wrongly use this plug to interrupt the ground connection and prevent buzz, but it is a VERY unsafe practice to break the ground connection using this plug without grounding the unit by another means.

Ground Lift Switch:

A switch that breaks the connection between the ground point in one circuit and the ground point in another circuit, for the purpose of eliminating hum or buzz caused by ground loops.

Ground Loop:

A situation caused when one or more electronic devices are connected to the same ground at different points. The devices operate at different ground potentials, which creates voltage along the ground, resulting in a low-frequency hum that can be annoying at best and cause damage to gear at worst. The best resolution for ground loops is to ground all devices at the same point using a central power source. An alternative solution is to break the loop via ground lift switches or plugs, but this should be avoided when possible as it is considered an unsafe management of electricity.

Group (or Grouping):

See “Subgroup.”

Group Delay:

In audio, group delay is a phenomenon within all electronic audio devices (e.g., speakers, amplifiers) in which different frequencies in the signal are output at slight delays from one another. In simpler terms, lower frequencies are delivered slightly more slowly than higher ones. In all devices, there is an inherent delay between input and output of the signal, but group delay specifically deals with the time delays between specific frequencies of the sound. The goal in any configuration is to keep the group delay as small as possible; in cases of extremely poor configurations, the delays between highs and lows can be audible.

Guitar Controller:

An electric guitar (or device played like a guitar) that transmits MIDI data that can be used to control synthesizers and sound modules.

Guitar Processor:

See “Effects Processor.”

Haas Effect:

(Also called Precedence Effect) Simply stated, a factor in human hearing in which we perceive the source of a sound by its timing rather than its sound level. In his research, Helmut Haas determined that the first sound waves to reach our ears help our brains determine where the sound is coming from, rather than its reflection or reproduction from another source. The reflection of the sound must be at least 10dB louder than the original source, or delayed by more than 30ms (where we can perceive it as an echo), before it affects our perception of the direction of the sound. This is what helps us distinguish the original sound source without being confused by reflections and reverberations off of nearby surfaces. Understanding the Haas effect is particularly useful in live audio settings, especially in large venues where loudspeakers are time-delayed to match the initial sound waves coming from the source.

Half Step:

A change in pitch equivalent to adjacent keys on a piano. Also known as a “semitone.”


See “Normalled.”

Hall Program:

A setting of a digital delay/reverb effects unit that approximates concert halls. Hall programs are characterized by pre-delay of up to 25 ms.

Hard Knee:

In compression, refers to a more abrupt introduction of compression of the signal once the sound level crosses the threshold. (See also “Knee.”)

Harmonic Distortion:

The presence of harmonics in the output signal of a device which were not present in the input signal, usually for the purpose of changing the instrument’s timbre.


Whole number multiples of the fundamental frequency that occur naturally within the playing of a tone. Mathematically, if the fundamental frequency is x, the harmonics would be 2x, 3x, 4x, etc. For example, if the fundamental frequency of the note played is 440Hz (or A-440), the harmonics would be 880Hz, 1320Hz, 1760Hz, and so on. The presence of harmonics in the tone is what creates the timbre of an instrument or voice.


In tape recording, an electromagnetic transducer that magnetically affects the tape passing over it. Recording/playback heads change the audio signal from electrical energy to magnetic energy and back, for recording and playback purposes. An erase head creates a powerful electromagnetic field to the tape to erase previous signals from the tape.


The difference in dB between normal operating level and clipping level in an amplifier or audio device.  Also describes the difference in dB between the peak levels of a recording and the point at which the signal distorts. (Also called “Margin.”)

Hertz (Abbreviated Hz):

1) The unit of measurement for frequency, specifically, the number of complete wave cycles that occur in a second (cycles per second). 1 Hz = 1 complete wave per second. 2) A popular rental car company (not typically used in recording except for transport to the studio).


In drum sets, double cymbal on a stand, usually positioned next to the snare, which can be played with a foot pedal and/or by the top cymbal being hit with a stick.


See “High Impedance,” “Impedance.”

High Impedance:

(abbreviated Hi-Z) Described as an impedance or resistance of several thousand ohms. In microphones, Hi-Z is typically designated as 10,000 or more ohms. (See also “Impedance.”)

High-Pass Filter:

An audio filter that attenuates signals below a certain frequency (the cut-off frequency) and passes signals with frequencies that are higher.

Highs or High-End:

Short for “high frequencies,” loosely the frequencies above 4000 Hz. Usually meant in the context of “highs, mids and lows” in an audio signal.


1) A speaker or speaker enclosure where sound waves are sent by a speaker cone or driver into a narrow opening which flares out to a larger opening. 2) One of several different types of brass musical instruments.

House Sync:

A reference signal such as SMPTE time code that is used to keep all devices in the room in sync.


1) The low-frequency pitch that occurs when power line current is accidently induced or fed into electronic equipment. The hum reflects the fundamental frequency of the current (60 Hz in the U.S., and 50 Hz in many European countries). 2) To vocalize a pitch without opening one’s mouth.


A variation of the cardioid microphone pick up sensitivity pattern in which the shape of the optimal pickup area is tighter and more directional than cardioid. Hypercardioid microphones are most sensitive directly on-axis in front of the microphone, and begins rejecting sounds between 90-150 degrees off-axis, depending on the tightness of the pattern.


An abbreviation for the term Hertz, or the unit of frequency.


An abbreviation for “Input/Output.” In audio, it refers to any device, program or system involving the transferring of electrical/audio signals or data.


See “Integrated Circuit.”

IM Distortion:

See “Intermodulation Distortion.”


Refers to the ability to localize a specific sound within the sound space. In recording environment, it refers to “placing” instruments within the stereo or surround field so that it when the sound is played through speakers, it fools our ears into thinking the sound source is in emanating from a specific point instead of from the speakers. In live audio and sound reinforcement, the principle of imaging is the same, the goal being to make the audience perceive the sounds as coming from performers on the stage, rather than from the speakers.


Refers to the resistance of a circuit or device to alternating current, which can be mathematically described as the ratio of voltage to current. Differences in impedance between devices in the studio can affect how they work together. Impedance is abbreviated by the letter Z, and measured in ohms (W).

In Line Console:

An audio mixing console that is designed and configured so each channel strip can be used for both recording and monitoring functions during multitrack recording. This configuration is in contrast to split mixing consoles, which requires separate channels on the board for recording and monitoring functions.

In Phase:

The desirable situation in which two or more devices (and their respective audio signals) are on the same side of the polarity spectrum, producing waveforms that do not conflict or cancel each other out.

In Port:

A jack on a MIDI device or computer that will accept an incoming data signal.


A characteristic of electrical conductors in which electrical charge (voltage) is produced or stored magnetically due to the natural resistance to change in the electrical current. Inductance is an electromagnetic principle that can either assist in audio applications (as in loudspeakers) or cause resistance (as in using speaker wire whose gauge is too low for the application).


A device (usually a coil of wire) that converts electrical energy into stored magnetic energy as electrical current passes through it. Commonly found in a variety of audio applications such as guitar pickups and loudspeakers.

Infinite Baffle:

A loudspeaker mount or enclosure designed so that sound waves coming from the front theoretically do not reach the back, preventing the sound waves from cancelling each other out. The term “infinite” comes from the idea that mounting the speaker on a wall with no end points would not allow sound waves to migrate behind it. Of course, this is physically impossible, so infinite baffles are designed to replicate this as much as possible. Examples of infinite baffles are mounting the speaker on a wall of an enclosed room, or building it inside a sealed cabinet large enough to prevent rear sounds from affecting the cone from the back.


The jack or physical location where a device receives a signal. Also refers to the incoming signal itself.

Input Impedance:

The opposition to current flow by the first circuits of a device.

Input Monitoring:

A setting on many DAWs that allows you to monitor the live input signal coming into the DAW (as opposed to the recorded signal).


An access in the signal chain (usually in the mixing console or virtually within a DAW) in which a device, signal processor or digital plug-in can be “inserted” into the circuit between pre-amplification and the channel or bus output. Commonly used to add processing such as reverb, compression or EQ to a channel or group of channels.

Instrument Amplifier:

A device that has a power amplifier and speaker to reproduce the signal put out by an electric instrument.

Instrument Out Direct:

Feeding the output of an electric instrument (like an electric guitar) directly to the recording console or tape recorder, as opposed to miking the amplifier.


A substance such as glass, air, plastic, etc., that will (for all practical purposes) not conduct electricity.

Integrated Circuit:

(Abbreviated “IC”) – A miniature circuit of many components set on semiconductor material, used in electronics. A fancy term for “chip” or “microchip.”


Any device or connection point that allows one unit to work, drive or communicate with another unit, or that allows a human to interact with a computer or other electronics. There are many examples of interfaces in professional audio situations, including MIDI (Musical Instrument Digital Interface); audio interfaces which connect audio inputs to your computer; and even your DAW program, which displays a screen that enables you to assign instruments, adjust settings, record, mix and playback. Even the mixing console is an interface of sorts, connecting the many elements of the control room.

Intermodulation Distortion:

Distortion caused by two or more audio signals of different frequencies interacting with one another. The sum and difference of the frequencies produce new (usually unwanted frequencies) that didn’t exist in any of the original frequencies.

Inverse Square Law:

A mathematical rule that describes an inverse relationship between one quantity and the square of another quantity. In plain English, one number goes down by a certain amount each time the other number doubles. In audio and acoustics, the inverse square law says that in an open sound field with no obstructions, the sound pressure level will drop by half (6dB) each time the distance from the sound source is doubled. (This equation is quite useful to audio engineers trying to provide sound in open-air settings, for example.)


The process of containing sound within a certain area so that it doesn’t interact with other sounds. For example, acoustically treated isolation booths are often used to record vocals or instruments in the studio to keep outside noises from bleeding into the recording microphone, or likewise to keep vocals or other sounds away from instrument mics during live recording sessions.


A connector mounted on the case of a device or on a panel.

Jam Sync:

A process available on some clock or syncing devices which reads an external time code and recreates (or “jams”) a new time code identical to the original external code for the syncing of devices. This function is mainly used for replacing code that has become degraded.


1) In music, the note scale in which a piece of music is written or played, identified by the first note (tonic) of the scale, as in, “Key of C.”  2) The control of a dynamics processing device by an external audio signal through the use of a side chain.  3) A digital or data code that unlocks the use of a device or software. Example: Pro Tools is licensed through an iLok ID via the use of a physical USB key.


Any musical instrument or computer controlled by pressing a key.

Keyboard Controller:

A piano-styled keyboard that sends out MIDI signals to control other MIDI devices. Most keyboard instruments are equipped with MIDI control capabilities, but dedicated MIDI keyboard controllers emit no audio signals, only MIDI data.


An abbreviation for kilohertz (1000 Hz, or 1000 cycles per second). Example: 2000 Hz = 2 kHz. Most commonly used in the studio for describing audio frequency ranges or digital sampling rates.

Kick/Kick Drum:

The bass drum on a trap drum set, so called because it is played with a kick pedal.


A function on a compressor that determines how abruptly or gradually compression begins once the sound level crosses the threshold. So-called because the graphic “bend” in the response curve is reminiscent of a knee. “Hard knee” refers to an abrupt activation of the compressor, while “soft knee” refers to a more gradual change.


Refers to almost any blending of similar multiple musical parts or sounds at once, often combined on one channel or assigned to one controller. In audio recording, layering usually involves recording similar takes of the same instrument or vocal (or duplicating parts with slight delays or chorusing effects) to create a fuller, richer sound than the vocal/instrument by itself. In sound design, it also refers to blending multiple samples (example: two or more drum sounds) to create a fuller sound.


The musical instrument that plays the melody, including the vocal.

Lead Sheet:

A shorthand form of music notation (similar to a chord chart) that displays the basic essential elements of a song so musicians can follow along without the full notation of every note or expression. Lead sheets most commonly include a melody line written in music notation with chord changes above the staff, and lyrics below it. (See also “Chord Chart.”)


Sounds from other instruments and sound sources that were not intended to be picked up by the microphone.


The amount of signal strength; the amplitude, especially the average amplitude.


A type of compressor that sharply reduces (limits) the gain of the signal when the audio level reaches a certain threshold, typically used to prevent overload and signal peaking. A compressor effectively becomes a limiter when its ratio is 10:1 or higher. (See also “Compressor.”)

Line Input (“Line In”):

An input designed to take a line level signal.

Line Level:

The standard audio signal level that runs through interconnecting cables in the studio or sound system, before the signal is amplified and sent to the speakers. Line level is often described in comparison to mic level or instrument level (which usually require preamplification to bring them up to line level).

Line Output (“Line Out”):

Any output that sends out a line level signal, such as the output of a console that feeds a recorder.


1) A term describing a space with a reverberant or reflected sound. In a “live” space, the sound waves are active or “live.”

2) Occurring in real time, as opposed to previously recorded.

Live Recording:

A recording session where all the musicians are playing at once with no overdubbing.

Live Room:

The large, main room of the recording studio where most of the instruments and/or vocalists perform. So called, not just because there is room for live performances, but because the room has been acoustically treated to produce a pleasing amount of live reverberation.


See “Low Impedance.”

Local On/Off:

A MIDI message that controls the internal sound module of a synthesizer or MIDI controller. “Local On” triggers the internal module when the keyboard is played; “Local Off” disconnects it. “Local Off” is frequently used to prevent unwanted looping of MIDI messages in some configurations, or when controlling the internal module via another controller.


1) Effectively, any piece of music or data that repeats endlessly. Before digital audio and sampling, loops were created by looping tape. Today, loops are used in samples to sustain a sampled note for as long as the note is triggered, while drum loops and other music loops are common in modern music production.  2) Another term for antinode, or the points of maximum displacement of motion in a vibrating stretched string or a sound wave.  (See also “Standing Wave.”)


A term referring to how the human ear perceives incoming sound waves. This term seems self-explanatory, but it’s deceptive. We commonly think of loudness as it relates to the volume of a sound, but this is an indirect relationship. In acoustic terms, volume is more about the amplitude of the sound waves, while loudness describes how our ears hear the intensity of those waves.

Low Impedance:

(abbreviated Lo-Z) Described as impedance of 500 ohms or less. (See also “Impedance.”)

Low-Frequency Oscillator (LFO):

A circuit that emits low-frequency electronic waveforms below the audible level of human hearing (20 Hz or less). This low-frequency waveform creates a rhythmic pulse that is used to modulate various parameters in the audio signal, such as pitch or volume. LFOs are frequently used in samplers, synthesizers and signal processors to create such effects as vibrato, tremolo, and phasing.

Low-Pass Filter:

An audio filter or device that attenuates signals above a certain frequency (the cut-off frequency) and passes signals with frequencies that are lower than the cut-off.

Lows or Low-End:

Short for “low frequencies,” loosely referring to bass-frequency signals below 250 Hz. Usually meant in the context of “highs, mids and lows” in an audio signal.

Magnetic Tape:

Recording tape consisting of a plastic strip coated by magnetic materials, finely ground iron oxide (rust) particles. Commonly used for analog recording.

Magnetic Tape:

Recording tape consisting of a plastic strip coated by magnetic materials, finely ground iron oxide (rust) particles. Commonly used for analog recording.


A natural attractive energy of iron based-materials toward other iron-based materials.


ee “Headroom.”


The characteristic of hearing by which loud sounds prevent the ear from hearing softer sounds of similar frequency. Also refers to the obscuring of softer sounds by louder ones.


1) The main output control of a console or DAW, setting the level of the mixed signal as it leaves the console. (Also called “master fader.”)

2) The final-mixed original recording from which copies are made.


The final process of fine-tuning and “sweetening” the mix on a song or collection of songs, from which the master will be created.


The grouping of a number of beats in music. (See also “Bar.”)


A slang abbreviation based on the prefix “Mega-, meaning 1,000,000. Often used as shorthand for megahertz (1,000,000 Hertz, Mhz) or megabytes (1,000,000 bytes, MB).


1) A device that measures and displays the signal level in audio or digital equipment. Meters usually measure peak values or RMS values. (See also “Peak Value,””RMS Value.”)

2) The rhythmic structure of music, typically describing the number of beats in a measure.

Mic, Mike:

Abbreviations for “microphone.”

Mic/Line Switch:

The selector switch on the input of a console channel that determines which input jack will feed the console; also the selector switch on an audio interface or other device that sets the input level to receive either a microphone level or line level signal.


A transducer which converts sound pressure waves into electrical signals.

Microphone (Mic) Input:

The input of a console or other device designated for a microphone signal.

Microphone (Mic) Level:

The very low audio voltage level emitted by a studio microphone. The signal must go through a preamplifier to be increased to line level before entering the console. (See also “Line Level,” “Preamplifier.”)

Microphone (Mic) Pad:

A setting on a microphone or preamp, or a separate adapter/connector, that reduces the level of the microphone signal before it enters the preamplifier to prevent overload.

Mid-Side Miking:

(Abbreviated M/S) A stereo coincident microphone placement technique in which one cardioid pattern microphone is aimed directly at the sound source, and a bi-directional microphone placed sideways and as close as possible to the first mic.


Musical Instrument Digital Interface, a digital data protocol that communicates performance information between musical instruments, sequencers and/or computer programs, conveying data on up to sixteen channels at once over a single connection.

MIDI Clock:

A clock signal conveyed by MIDI that is used by the connected sequencers and musical devices to stay in sync with one another. Not to be confused with MIDI time code (MTC), MIDI clock is tied to the Beats-Per-Minute (BPM) tempo, advancing 24 steps per quarter note.

MIDI Controller:

Can refer to two different elements of MIDI, depending on the context. 1) A device or software that sends MIDI data to connected devices, either through pre-programmed sequencing or through live performance by a musician. 2) Any of a number of smaller controls on a MIDI device that is assigned to control specific parameters of the sound or performance.

MIDI Interface:

A device that converts a MIDI signal into the digital format of a computer so it can store and use the MIDI signal.

MIDI Sample Dump Standard (SDS):

A sub-protocol that was added into MIDI to enable the transfer of digitally recorded samples between instruments, storage units or sound modules without converting them to analog.

MIDI Sequencer:

A device or software that can record and play back MIDI data, controlling the performance of MIDI musical instruments or devices in a series of timed steps. MIDI sequencers can exist on board MIDI controllers, keyboards or workstations, as standalone devices, or as computer software.

MIDI Thru:

A port that puts out a MIDI signal that is the same as the incoming MIDI signal, effectively relaying the signal to another device without altering or changing it.  (Many MIDI devices have three MIDI ports: In, Out and Thru.)

MIDI Thru Box:

A unit with one MIDI In Port and several MIDI Thru Ports to relay the MIDI signal to multiple devices. MIDI users often prefer this as an alternative to “daisy chaining” devices, which can cause slight delays in the MIDI signal.

MIDI Time Code (MTC):

The translation of the information in SMPTE time code into MIDI data, enabling MIDI sequencers and connected devices to sync with SMTPE code (usually in relation to video). (See also “SMPTE Time Code.”)


Abbreviation for “mid-range frequencies,” the audio frequencies from about 250 Hz through 6000 Hz. Meant in the context of “highs, mids and lows” in an audio signal.


1) The blending of audio signals together into one composite signal.

2) Can also refer to the blending of a portion of an effected audio signal back into the direct signal.

Mixdown or Mix Down:

The processes of creating a final mix by combining multiple audio tracks into a single track (or two-channel stereo track) prior to the mastering stage. This can include the traditional method of mixing the multiple channels of analog tape into a two-track master, or the more modern method of creating a digital mixdown using a DAW (which is often referred to as “rendering”).


Refers to any process in which a parameter of one signal is systematically affected by the introduction of another signal. In audio, this results in a change in the sound.

Modulation Noise:

Noise that is present only when the audio signal is present.


A self-contained group of circuits and controls. In the recording studio, modules are often contained in interchangeable housing for installation on rack mounts, and can include amplifiers, equalizers, effects processors and sound modules (MIDI instruments to be activated by an external controller). In the digital space, plug-ins, software synths, samplers and plug-ins are also described as modules.


(Abbreviated “Mono”) Describing an audio signal coming through a single, as opposed to stereo, which is two channels. (See also “Monophonic.”)


1) To listen to the music for the purpose of checking quality or avoiding peaks. 2) A speaker in the studio (usually one of a pair) that is used to listen to the audio signals. This can include studio monitors in the control room for listening to the mix, and headphones in the booths or live room for the performers to hear a mix of the tracks while they are performing.

Monitor Mix:

A mix of the live and/or recorded audio signals that is fed to the musicians so the can hear the music while performing, whether live onstage or in the studio. Monitor mixes are on a separate signal path from the main mix (often controlled by a separate, smaller console) and do not affect the FOH mix (in live audio) or the signal going into the multitrack recorder/DAW. In live performance settings, the monitor mix is often controlled by a separate audio engineer running a separate sound board.

Monitor Path:

A signal path separate from the channel path that allows the engineer to listen to what is being recorded without affecting the signal being fed to the multitrack recorder or DAW. (See also “Channel Path.”)

Monitor Section/Monitor Mixer Section:

The section of the console that is used to create a rough mix so the engineer can hear what is being recorded without effecting the levels being fed to the multitrack recorder or DAW.


See “Monaural,” “Monophonic.”


(Abbreviated “Mono”) 1) A single sound source or single-channel transmission (as opposed to stereo). 2) A melody line in which only one note at a time is played. 3) Describing an instrument or synthesizer setting that only plays one pitch (or “voice”) at a time. (See also “Voice.”)

Moving Coil Microphone:

See “Dynamic Microphone.”

Moving Fader Automation:

A feature in some consoles in which fader changes can be pre-programmed to occur automatically during playback of a multitrack recording.


A small device that tests electrical voltage, current, and resistance. Multimeters are useful in recording studios for calibrating electrical systems and troubleshooting problems.


Refers to the ability of a synthesizer or module to play several different sounds, patches or “timbres” at once.

Multitrack Recording:

(Also called tracking or multitracking) The heartbeat of the recording studio, multitrack recording is process of recording a collective of sound sources onto separate tracks, each with its own audio channel, then combining the tracks to play back simultaneously. Recording can be done either one track or instrument at a time (to be combined later) or by recording the performers onto separate tracks as they play together live. These signals were originally recorded onto multitrack analog tape, but today they can also be recorded digitally as separate audio files into a digital audio workstation (DAW).

Multitrack Tape:

A piece/reel of magnetic tape which can be used to store two or more discrete signals in sync with each other.

Mute Switch:

A switch on a console or other piece of audio equipment that turns off the input or output, or a matching button on the virtual audio control space of a DAW. The individual channels on a console each have a mute switch that can cut the signal for that channel.

Nanowebers per Meter (NW/m):

The standard unit in measuring the amount of magnetic strength on analog tape. A Weber is a unit of magnetic strength, but it is too large a unit to apply to the magnetism in tape recorders, so nanowebers is used instead. Nanowebers per meter of tape effectively describes the signal strength that is being recorded to tape.

Narrowband Noise:

Noise (random energy) that occurs over a limited frequency range.

Near Field:

The area between 1-5 feet from the sound source. Studio monitors are generally considered “near-field” speakers because they are meant to be listened to at close range. (See also “Far Field.”)

Near-Coincident Miking:

A stereo miking technique in which two microphones are placed near each other at an outward angle to create a stereo image (as opposed to “Coincident Miking” which angles the microphones toward each other).  Common versions of near-coincident miking include DIN stereo (90-degree angle, 20cm apart), NOS stereo (90-degree angle, 30 cm apart) and ORTF (110-degree angle, 17 cm apart).

Negative Feedback:

A portion of the output signal that is fed back to the input of an amplifier with its phase inverted from the original output signal. This has a dampening effect on the output, effectively cancelling out a portion of the volume.


Describes any unpleasant, objectionable or unintended sound frequencies present in the audio signal. All electronic equipment produces some type of noise, which may be described as a hiss or buzz that can be heard during quiet or otherwise silent passages. (See also “Noise Floor.”) Bad connections, improper grounding, radio interference and other issues can also cause introduce noise into the signal. Engineers may also deliberately run a noise signal through a sound system for testing purposes. (See also “White Noise, “Pink Noise.”)

Noise Floor:

The level of the noise present below the audio signal, measured in dB. Every electronic device emits a minimum level of noise, even when no audio is traveling through it; this is described as its noise floor. Generally speaking, the lower the noise floor in these devices, the higher the quality of the device. The noise floor also translates to the recorded signal; the noise floor of a recording is the sum of all the noise generated by connected devices. The objective is always to keep the noise floor as low as possible.

Noise Gate:

A gate that is used reduce audible noise by automatically turning off an audio channel when the signal is not present.

Noise Reduction:

Any of a number of processes to remove noise from a signal, device or system.

Non-destructive Editing:

A feature in recording systems (most common in Digital Audio Workstations, or DAWs) in which the original signal or content stays intact while edits are performed, allowing the engineer to revert to the original version at any time. (Sometimes also called “Nonlinear editing.”)


See “Omnidirectional.”


To apply a fixed amount of gain to audio so that the highest peak is set at the highest acceptable recording level.


Describes the configuration within a patch bay in which the jacks form a connected pathway until a patch cord is inserted to change the path. When a patch bay is “full-normalled,” the connection is altered by inserting a cord into either the input or output side; when it is “half-normalled,” the path changes only when a cord is plugged into the input. “Non-normalled” or “open” means there are no internal connections, and each input sends the signal through its corresponding output.


A narrow band of audio frequencies.

Notch Filter:

A band stop filter set to reject frequencies within a very narrow band. So called because the attenuated frequency band looks like a “notch” in the spectrum it is displayed visually (for example, in an EQ plugin). (See also “Band Stop Filter.”)


See “Nanowebers per Meter.”

Nybble (or Nibble):

One half byte of computer data, or 4 bits.

Nyquist Frequency:

In digital recording, the highest frequency that can be recorded and reproduced properly, equivalent to a one-half the sampling rate. (For example, with the common sampling rate of 44,100 kHz per second, the Nyquist frequency would be 22,050 kHz.) Aliasing begins to occur with frequencies that exceed this threshold. (See also “Aliasing.”)

Nyquist Rate:

The lowest sampling rate that can be used to record and reproduce a given audio signal, equivalent to twice the highest frequency. If the highest frequency found in an analog signal or sound is 18,000 kHz, theoretically the signal must be sampled at a minimum of 36,000 kHz per second—otherwise, the signal is considered to be undersampled and aliasing will occur. This is essentially the inverse principle of the Nyquist Frequency. (NOTE: the sample rate of 44,100 kHz/second is considered the standard sample rate because it easily covers the upper range of human hearing, which is about 20,000 kHz.)


An interval or difference of pitch of 12 half-steps. In our standard tuning system, the higher note in an octave is exactly double the frequency of the lower note.

Off Axis:

Veering away from the imaginary line (axis) directly in front of the receiving end of a microphone. Measured as degrees of an angle. (For example, a sound coming from directly behind the microphone is said to be 180 degrees off-axis.)

Offset Time:

1) The SMPTE time that will trigger a MIDI sequencer to begin. 2) The amount of position difference needed to get two reels to play the music in time.

Ohm (W):

The unit used to measure the amount of opposition (impedance) to electrical current flow in a signal or device. (See also “Impedance.”)

Ohm’s Law:

The mathematical relationship between voltage, current and resistance.


A prefix meaning “all.”

Omni Mode:

A setting that enables a MIDI device to recognize and respond to all MIDI channels at once.

Omnidirectional Pattern:

In microphones, picking up evenly from all directions (sometimes also called “Nondirectional”). 2) In speakers, sending out the signal evenly in all directions.

On Axis:

The position directly in front of the diaphragm of a microphone, in line with its movement.

Op Amp:

See “Operational Amplifier.”

Open Circuit:

An electrical circuit that is disconnected, interrupted or incomplete, preventing the flow of electricity.

Operating Level:

(Sometimes called “Reference Level“) The maximum level that should not be exceeded in normal operation.

Operational Amplifier:

(Abbreviated “Op Amp“) An amplifying circuit used in most audio and electronic devices.


1) A tone generator in a synthesizer. 2) A device that puts out test tones at various frequencies.

Out Of Phase:

1) Being similar to another signal in amplitude, frequency and wave shape but being offset in time by part of a cycle. 2) Having the opposite polarity.

Outboard Equipment:

Equipment that is used with, but is not a part of, a console.


1) The jack or physical location of where a device sends out a signal. 2) The signal put out by a device.

Output Impedance:

The opposition to the flow of electrical current by the output circuits of an amplifier (or other device).

Output Level:

The signal level at the output of a device.


The process of recording an additional musical performance over an existing recording, usually on its own track. Overdubbing has become a common recording technique with the advent of multitrack recording, first on multitrack analog tape, and more recently via computers and Digital Audio Workstations (DAWs).


Any harmonic in a tone except the fundamental frequency. (See also “Partial.”)


1) A device or circuit that attenuates an incoming signal, usually to prevent overload of an amplifier that follows along the signal path. (Also sometimes called “Attenuator pad.”)  2) A device with a surface that can be hit by a drum stick; hitting the pad produces an output signal pulse (or MIDI command) that causes a drum machine or synthesizer to sound a drum sound. 3) A type of synthesizer patch/program used to create sustained background or atmospheric sounds.

Pan (Panning):

The process of “placing” a particular sound within the stereo field. This is accomplished by controlling the balance of the signal between the left and right speakers so the ear hears the sound as coming from a particular point in the sonic space between left and right. This sonic space is sometimes called the “stereo panorama,” from which the word “panning” is derived. In surround sound, panning occurs in a 360° sound space, not just left-right.

Panpot (or Pan Pot):

Short for “Panoramic Potentiometer,” a panpot is a knob in the channel strip that controls the panning of the audio signal in the stereo (or surround) space by controlling how much of the signal is sent to each speaker or channel.

Parallel Jacks:

Several jacks that are wired so that each connection is wired to the corresponding connection of other jacks.

Parallel Port:

A connector that is able to transmit and receive digital data at the same time though different pins.


Each characteristic of a sound, signal or device that is possible to change.

Parametric EqualizationParametric EQ:

An equalizer in which all parameters of equalization can be adjusted to any amount, including the center frequency, the amount of boost or cut, and the bandwidth.


1) Another word for overtone. 2) One of a number of sine waves that makes up a complex sound, helping to define the timbre. This concept is a key part of creating sounds in synthesizers: in additive synthesis, a number of partials are combined to create a certain tone.

Pass Band:

The frequency range of signals that will be “passed” by a filter, rather than reduced.

Passive Device:

A component that does not generate or control electrical current (as opposed to an “Active Device”). In audio applications, this usually refers to a piece of gear that does not include an amplifier as part of its design. For example, active speakers are self-powered, while passive speakers require an external amplifier in order to reproduce sound. (See also “Active Device.”)


1) To route or reroute the signal in an audio system (such as a console) by using short cables with plugs inserted into jacks. 2) A sound setting or program on a synthesizer.

Patch Bay (or Patchbay, Patch Field, Patch Panel):

A panel or component containing a series of jacks with connections for most of the inputs and outputs of the console and components in the studio, used for the purpose of organizing, managing and regulating signal flow.

Patch Cord (or Patch Cable):

An insulated cable with plugs on each end used to route audio signals. Patch cords are typically thought of as short cables used to make connections in the patch bay (hence the name); however, patch cords facilitate almost any kind of audio connection between devices, can come in a wide range of lengths, and can include a number of different types of connectors.

Patch Field:

See “Patch Bay.”

Patch Librarian:

A computer program allowing for the storing of sound patches outside of a synthesizer via MIDI.

Patch Panel:

See “Patch Bay.”


Short for Signal Path, the way in which current does or may travel in a circuit or through a device.


See “Pulse Code Modulation.”

Peak Filter:

An EQ circuit/filter that boosts or cuts the middle (center frequencies in an audio signal, as opposed to high-pass or low-pass filters. (NOT to be confused with amplitude peaks.)

Peak Meter:

A meter which detects the absolute peak value of a waveform, as opposed to the RMS value. (See also “Peak Value,” “Root-Mean-Square,” “RMS Meter.”)

Peak ValuePeak Value (also called Peak Level):

The measure of the maximum positive or negative value (amplitude) of a waveform at any moment. In audio, this is visually depicted as the farthest point of the waveform above or below the zero axis.

Peak-to-Peak Value:

The measure of the total amplitude between positive and negative peaks in an audio signal. Equal to twice the peak value for a sine wave. (See also “Peak Value.”)

Pedal Board:

A board with several guitar pedals attached and inter-connected so that a guitar player can conveniently activate a number of different effects.

Phantom Power:

A system used to supply DC voltage to condenser mics and other components through the audio cables, eliminating the need for external power supplies.


A measurement (expressed in degrees) of the time difference between two similar waveforms.

Phase Addition:

The increased audio energy that happens when waveforms are in similar phase relationships, resulting in an increase in volume up to twice what it should be.

Phase Cancellation:

The opposite of phase addition, this is the reduction of energy that occurs when two similar waveforms that are out of phase with one another and begin cancelling each other out, either greatly reducing or eliminating the volume. When two identical wave forms are completely out of phase (by 180 degrees), the result in theory is a total silencing or cancellation of the signal.

Phase Distortion:

A change in the sound because of a phase shift in the signal. Sometimes used in synthesizers as a method of altering the wave shape or adding harmonics to the sound.

Phase Lock:

Any of a number of processes used to help synchronize signals or devices by correcting phase differences. For example, in analog tape machines, phase locking helps to keep multiple machines synced together by sensing phase differences in the playback of pilot tunes by the two machines and adjusting the speed to eliminate the phase difference. In synthesizers, phase locking controls one tone generator so that it begins its waveform in phase with the signal from another tone generator. Phase-locked loops (PLL) are reference signals used in the clock functions of electronic devices.

Phase Reversal:

A change in a circuit to get the waveform to shift by 180 degrees.

Phase Shift:

A delay introduced into an audio signal measured in degrees delayed.

Phase-Locked Loop (PLL):

See “Phase Lock.”


An effects sound created by varying the phase shift of an audio signal, then mixing it with the direct signal.


A unit of apparent loudness, numerically equal to the same number of dB as a tone playing at 1000 Hz. For example, a sound is said to be 60 phon if it is perceived to be as loud as a 1000-Hz tone playing at 60dB.

Phone Plug (Jack):

A plug (or its mating jack) with a diameter of 1/4 inch and a length of I 1/4 inches used for interconnecting audio.

Phono Plug:

See “RCA Plug.”


1) A device on an electric guitar or other instrument that puts out an audio signal according to the string motion on the instrument. 2) See “Contact Microphone.”

Pickup Pattern:

The shape of the area in front of or around the microphone from where it evenly picks up sound. Many use this term interchangeably with “polar pattern,” but a polar pattern gives more detail about microphone sensitivity. (See also “Polar Pattern.)

Pinch Roller:

A rubber (or plastic) wheel on a tape recorder that pinches the tape between it and the capstan, allowing the capstan to pull the tape.


See “Bouncing.”

Pink Noise:

A noise signal similar to white noise, containing all audible frequencies, but with equal energy per octave as opposed to all frequency bands. Engineers frequently use pink noise as a tool to tune and calibrate audio equipment. (See also “White Noise.”)


1) The perception of frequency by the ear (a higher or lower tone of music). 2) A control on a tape transport which adjusts the speed slightly up or down, changing the pitch and time of the music.

Pitch-to-MIDI Converter:

A device that detects pitch in an analog audio signal and translates it into MIDI information. (Also called “Audio-to-MIDI-Converter.”)

Pitch-to-Voltage Converter:

A device that detects the frequency of an audio waveform and changes it into a control voltage, which is in turn fed to an oscillator that produces a pitch at the same frequency.

Plate Reverb:

A device that produces artificial reverberation by sending vibrations across a metal plate via a transducer similar to a speaker driver. Physical plate reverbs today are considered a vintage form of artificial reverb; nowadays, most plate reverb effects are emulated digitally by plugins or reverb units.


1) The reproduction of recorded audio. 2) In motion picture or video production, the reproduction of the music over loudspeakers so the performers/musicians can perform in time to the music for the camera.

Playback Head:

A transducer that converts magnetic flux recorded on tape into an audio signal for playback.

Playback Mode:

A configuration on a console that allows quick playback of the signal previously recorded on tape or via DAW via the monitor mixer.


1) See “Take.” 2) A user-defined selection of songs; a feature available on most streaming and digital media players.


A connector, usually on a cable, that mates with a jack.

Polar Pattern:

1) In microphones, a graphic display of the area around the microphone that is sensitive to sound waves, detailing the audio output levels in dB of sound arriving from different directions. Similar to “Pickup pattern,” but more specific. 2) In speakers, a graphic display of the speaker’s dispersion of sound.


The direction of current flow or magnetizing force.

Polarizing Voltage:

In condenser and electret microphones, the introduction of a small amount of electrical current to create the magnetism by which the capacitor converts audio signals to electrical current. In condenser microphones, polarizing voltage is provided externally (see also “Phantom Power”); in electret microphones, the polarizing voltage is permanently impressed on the condenser during manufacturing.

Pole Pieces:

Iron or other magnetic material that conducts magnetic force for use in transducers like record heads, playback heads, microphones, speakers, etc.


Able to play more than one pitch or “voice” at the same time. A term commonly used to describe synths and keyboards. (See also “Voice.”)


See “Bouncing.”

Pop Filter:

A device that is placed over a microphone or between the microphone and vocalist to prevent loud “pop” sounds created by the vocalist’s breath directed toward the microphone.


1) A connection point in computer or electronic device for transmitting and receiving digital data, similarly to how a jack receives and transmits audio signals.  2) An opening or vent in a speaker case that resonates with air movement in the speaker, used in bass reflex speakers and woofers to enhance low frequencies.


A pitch change that smoothly glides from one pitch to another. Also refers to the synthesizer mode or MIDI command that allows or causes this to happen.


Short for either “Post Production” or “Post-Fader.” (See both entries.)


Refers to an aux send position or setting that places the send after the channel fader within the signal path. Sending a signal post-fader means the fader itself affects the level of the send signal, as opposed to pre-fader. (See also Pre-Fader.)


Refers to the work of adding tracks, editing and other fine tuning after primary recording or filming has taken place. Post-production in recording includes such things as additional overdubs, editing, mixing and mastering. Post-production in film includes a wide range of additional audio and visual effects.  NOTE: We mention film in this context because film post-production includes a lot of audio work (e.g., voiceovers, foley, audio mixing and editing) to the point that many audio engineers are involved in film post-production as a full-time career.


A segment of blank tape (or track silence, on a DAW) that runs past the end of the recording. (See also “Pre-Roll.”)


See “Potentiometer.”


(Abbreviated “Pot“) Often thought of as a fancy word for “knob,” a potentiometer is basically any mechanism that controls input or output voltage by varying amounts (for example, panning a signal left/right, volume control, or the amount of signal sent to an aux send or bus. Potentiometers can be knobs or faders, meaning that almost every control on a console that isn’t a button or switch is a potentiometer. However, many engineers commonly refer to faders as “faders” and knobs as “pots.”

Power Amplifier:

(abbreviated “Power Amp”) A device that amplifies a line level signal to drive a speaker or set of speakers.  (See also “Line Level.”)

Pre Emphasis:

A boosting of high frequencies during the recording process to keep the audible signal above the noise floor.

Pre Fader:

Refers to an aux send position or setting that places the send before the channel fader within the signal path. Sending a signal pre-fader means the fader does not affect the level of the send signal, as opposed to pre-fader.


A parameter on a reverb unit or plugin that determines the amount of time (delay) between the original dry sound and the early reflections of reverberation. This feature is often used to simulate the natural acoustic properties of a room, but can also be used to create interesting unnatural effects.


(Also called “Forward Echo”) A compression artifact that often occurs in digital audio in which an “echo” of a sound (or part of a sound) is heard ahead of the sound itself, often due to the data inconsistencies in certain compressed digital formats. A type of pre-echo can also sometimes occur in the end product of a recording, occurring on tape as a result of low-level leakage caused by print-through, and also on vinyl records due to physical differences and/or deformities in the grooves between silence and a loud transient. In digital formats, pre-echo is generally an unwanted problem that requires additional signal processing to resolve—but in some cases it can also be used on purpose as a sound effect (not to be confused with “Reverse Echo”).

Pre-Fade Listen (PFL):

A function on the channel strip of a mixer or DAW that allows a channel signal to be heard and often metered before the channel fader.

Pre/Post Switch:

A switch on the input module that determines whether the send control comes before or after the main channel fader in the signal path (See also “Pre-Fader,” “Post-Fader.”)

Preamplifier or Preamp:

A low-noise amplifier designed to take a low-level signal (for example, from a microphone) and bring it up to normal line level before sending it into the mixing console.

Precedence Effect:

See Haas Effect.”


1) The process of mixing a set of tracks as group, then managing the mixed group in the context of the other tracks by routing them to an auxiliary channel. Consolidating tracks by bouncing is a form of premixing, but a premix is not necessarily pre-recorded. (See also “Bouncing.”) 2) An important part of film post-production in which the process of mixing a section of audio for combination with the others. Dialogue, Foley, SFX and music may all be premixed before being combined together under the video.


1) In amplification and mixing, the boosting of upper-mid frequencies to cause a sound or instrument to cut through, creating the impression that the sound source is more “present,” right next to the listener. 2) See “Room Tone.”

Presence Frequencies:

The range of audio frequencies between 4 kHz and 6 kHz that when boosted, can increase the sense of presence, especially on voices.


A factory programmed set of parameters on a synth, signal processor, plug-in or other electronic device.

Pressure Microphone:

(Also called “pressure operative microphone”) – A microphone whose diaphragm responds to incoming sound wave pressure as it works against the normal or controlled air pressure inside the microphone case. This design makes the diaphragm sensitive to pressure regardless of direction, giving it an omnidirectional pickup pattern. (See also “Omnidirectional Pattern.”)

Pressure Sensitivity:

See “Aftertouch.”

Pressure Zone Microphone:

See “Boundary Microphone.”

Pressure-Gradient MicrophonePressure-Gradient Microphone:

(Also called “Velocity Microphone“) A microphone whose diaphragm is exposed front and back, with diaphragm movement being caused by the pressure difference between its front and back. This creates a bi-directional or “figure-8” pickup pattern (See also “Bi-Directional Pattern.”)

Print Through:

The unwanted transfer of magnetic flux from one layer of analog tape to another.

Pro Tools:

Avid’s trade name for its digital audio workstation (DAW) that has become an industry standard in professional recording studios.


See “Signal Processor.”


See “CPU.”


In music, the producer is the director of an audio recording project; the person responsible for getting a final product of desired quality within a budget.


1) The collective actions that go into producing music. 2) Describing the quality of a recording—the end result of production decisions during the recording and mixing process.

Production Studio:

Broadly speaking, any space dedicated to production within the arts, for example, film/video, animation or post production. In the context of audio, a production studio is effectively a recording studio that specializes in the assembly and mixing of commercials and radio programs from pre recorded music and effects with newly recorded dialogue.

Program Change:

A MIDI message that tells the receiving device to change presets.


Able to have the parameters changed by the user, especially in a computer controlled device.


A set of instructions for the user to follow, which appears on a computer screen.


In digital and information technology, a set of rules governing the structuring and transmitting of data in a standardized format so all related devices can properly interpret the data.

Proximity Effect:

The natural boost in the microphone’s output for bass frequencies as the mic is placed closer to the sound source.


The study of how humans perceive and respond to sound, not just in the context of interpreting the physical sound waves, but also taking psychological and emotional factors into account. This branch of science is helpful to audio engineers in understanding how the brain interprets various sounds and frequencies.


Any circular piece of metal, fiber, rubber, etc., which drives something from a rotating power source. A common example in the recording studio is the puck in a rotating Leslie speaker.


1) The steady beat in music based on its tempo, whether audible or perceived. 2) A type of sound wave commonly created and manipulated by synthesizers whose waveform is characterized by sharp rises and drops in amplitude like a square wave, but whose peaks are shorter than its troughs, giving the wave a pulse-like feel. Also called “Pulse Wave.”

Pulse Code Modulation (PCM):

A process by which analog signals are translated to digital code. This is done by taking samples of the amplitude of the analog signal at regular rapid intervals, then translating it into binary numbers as a digital representation of the original signal. The faster the sample rate, the better the digital reproduction. PCM is the most common form of A/D conversion in digital audio.

Pulse-Width Modulation (PWM):

In synthesized music, the process of using a control voltage to vary the width of a pulse wave form, essentially switching between square waves and pulse waves. This has the effect of creating richer timbres, giving sounds a thicker, more lush feel, or of giving a digital sound more analog properties.

Pumping and Breathing:

In studio jargon, an effect created when a compressor is rapidly compressing and releasing the sound, creating audible changes in the signal level. “Pumping” generally refers to the audible increase of sound levels after compression has taken place; “breathing” refers to a similar effect with vocals, raising the signal volume just as the vocalist is inhaling. Pumping and breathing is a sign of cheap compression or over-compression, and is usually undesirable, although some engineers and musicians use it on purpose occasionally to create a particular effect.

Punch In/Punch Out Recording:

The process of activating and/or deactivating the record function on tape or DAW during playback of a passage, usually as the performer plays/sings along. This can be used either as a method of doing quick overdubs, or as a way of getting a better take on a certain passage without having to start the track from the beginning.

Pure Tone:

A tone consisting of only the fundamental frequency with no overtones or harmonics, graphically represented as a simple sine wave.


Abbreviation for Crown Audio’s Pressure Zone Microphone. (See also “Boundary Microphone.”)


(Also called “Q Factor”) – Stands for “Quality Factor,” defining the bandwidth of frequencies that will be affected by an equalizer. The lower the Q, the broader the bandwidth curve of frequencies that will be boosted or cut.


A now rarely-used system of four-channel sound where the channels are designated as left front, left back, right front, right back, intended to deliver sound from all four corners of a room. Quadraphonic sound was a precursor to the surround-sound systems of today.


1) In digital music, the process of adjusting the rhythmic performance of music by moving the notes to precise locations on the time line, effectively “rounding” the note occurrences to the nearest defined increment. 2) In analog-to-digital conversion, the use of the same mathematical quantization principles to convert an analog signal into a smaller set of steps (a digital quantity).

Quantization Distortion/Quantization Error:

The effective “error in translation” between an analog signal and its sampled counterpart due to the rounding of a large number of analog values to the nearest digital quantity. This often results in additional random frequencies in the sound, often heard as noise.

Quantization Noise:

The modulation noise in a signal resulting from quantization error.

Rack EarsRack Ears/Rack Flanges:

Mounting brackets that can are attached to equipment so it can be mounted in a standard equipment rack.


Describing outboard gear that can be housed in an equipment rack.

RackRack (or Equipment Rack):

A cabinet or framework with rails, used to mount and house various components of outboard gear.


The angle and pattern of coverage of a speaker.

Radiation Pattern:

A graphic depiction of speaker coverage. This is not unlike the polar pattern of a microphone, with the exception that a polar pattern describes the area where sound arrives at the microphone, while a radiation pattern describes how sound is dispersed from the loudspeaker.

Ramp Wave (Sawtooth Wave):

See “Sawtooth Wave.”

Random Access Memory (RAM):

The “short-term” memory in a computer that is used in tandem with the processor for performing immediate tasks (as opposed to hard-drive storage memory where projects are saved and recalled). In the recording studios, the more RAM a computer has, the more ability it has to handle large amounts of data at a time (for example, in multi-track recording or working with virtual MIDI instruments).

Random Note Generator:

A device that generates random pitches at a set rate, used in synthesizers.


To perform a spoken rhythmic part to a music or percussion performance.


The reduced density of air particles during the trough of a sound wave; in the context of “compression and rarefaction,” it is the opposite of compression. (See also “Compression.”)

Rated Load Impedance:

The input impedance, or opposition to current flow by an input of a device, that a piece of equipment is designed to feed.

RCA Plug (jack):

(Also called Phono Plug) A common audio connector found on most stereo systems with a center pin as one connection and an outer shell as the second connection.


To retrieve information bits from a storage device; in digital audio, the reproduction of digital signals.

Read Only Memory (ROM):

A type of data storage that cannot be erased or reprogrammed by the user. The most common form of ROM in audio/video settings today is optical storage media (i.e, CD, DVD, CD-ROM and DVD-ROM).


Popular music software program from Propellerhead Software.  It offers the digital equivalent of hardware synthesizers, samplers, signal processors, sequencers and mixers. Reason works as a virtual music studio, or as a set of virtual musical instruments which can be played live or used with other sequencing software.

Record Head:

A device on an analog tape machine that changes electrical current to magnetic energy; the changes of the magnetism match the waveshape of the audio signal fed to the head.

Record Level:

A control on a tape machine that determines the amount of magnetic flux recorded on the tape, or the DAW control that determines the level of the digital signal recorded to the sound file.

Record Monitor:

On some tape machines, a switch position that allows the VU meter and sound output of the tape machine electronics to monitor the input signal to the tape machine.

Record Ready:

A control state of a multitrack tape recorder where the designated track will begin recording when the record function of the tape recorder is activated.

Recording Bus:

A bus that sends a mix signals from the console channels to the multitrack recorder or DAW. (See also “Bus.”)


1) The hub and flanges onto which analog tape is spooled; recording and playback involves unspooling the tape from one reel and onto another. 2) Sometimes also called “demo reel,” a compilation of audio or video that demonstrates the abilities of a musician, audio engineer, actor, or other audio/visual professional. Unlike a demo, which is intended to pitch one or more songs, a reel is a demo intended to promote the abilities of the professional rather than the product itself. The term itself is a holdover from the days when this promotional material was delivered on reels.

Reference Level:

1) A standard baseline level of volume used to measure how much level is present in dB above or below the baseline. 2) See “Operating Level.”

Reference Tone:

A single-frequency tone (often at 1000 kHz) used to calibrate the levels of sound equipment; the tone used to set reference level. (See also “Test Tones.”)

Reflected Sound:

Sound that reaches a microphone or listener after one or more reflections from surrounding surfaces.


In acoustics, the bouncing of sound waves off of a flat surface, as opposed to absorption. Reflection can have a great impact on how we perceive the collective sound; reflected sounds from a distance is perceived as echo, while reverberation is created from thousands of reflections. (See also “Absorption,” “Early Reflection,” “Echo,” “Reverberation.”)

Regulated Power Supply:

A device to supply power to electronic equipment whose output voltage will not fluctuate when more equipment is turned on, or if there is a change in voltage of the power line. A regulated power supply is designed to protect sensitive electronics from destructive power surges.


An electromagnetically activated switch that connects or disconnects two terminals when a control voltage is applied.


The final stage in the four stages of a sound (Attack, Decay, Sustain and Release, or ADSR); the release of the sound describes the rate at which the volume drops to zero as the sound stops playing. In synthesizers, describes the volume reduction of the sound once the key is released.

Release Time:

In dynamics signal processors, the time it takes for the output signal to return to original levels when the input signal crosses the designated threshold.


1) A device that controls the functions of another device wirelessly. 2) Describing on-site recording, as opposed to recording in the studio.

Residual Magnetization:

The amount of magnetism left in a magnetic material after the magnetizing force is removed. Residual magnetism can accumulate in tape machines over time, either creating distortions and noise in the sound output or partially erasing the tape.

Residual Noise:

The noise level left on recording tape after it has been erased.


The opposition of a substance to the flow of electrical current, measured in ohms.


An electrical component with a specific amount of resistance to electrical current, used within the circuit to regulate the flow of current.


1) The natural tendency of physical substances to vibrate with more energy at certain frequencies. The principle of resonance is a key element in the design of acoustic instruments; for example, the hollow chamber of a guitar or violin is designed to resonate with the vibrations of the string. Resonance also plays a role the acoustic design of a space, and even in developing good vocal technique to project the voice.

Resonant Frequency:

A frequency at which a physical item vibrates naturally.


To vibrate at the resonant frequency. Also refers to the lingering reverberation that causes a sound to continue after the sound source has stopped. This continuing sound is due to the sympathetic resonance of nearby objects.


See “Auxiliary Return.”


1) Short for “Reverberation.” (See “Reverberation.”) 2) A signal processor or plug-in that creates artificial reverb to a signal.

Reverb Time (RT):

The time it takes for the reverberation or echoes of a sound source to die out after the direct sound has stopped. Specifically, the reverb time is measured between the point at which the sound source stops and the point at which the reverberation levels fall by 60 dB.

Reverberant Field:

Describes the space that is far enough from the sound source that the reverberations are louder than the direct sound.


The persistence of a sound after the source stops emitting it, caused by many discrete echoes arriving at the ear so closely spaced in time that the ear cannot separate them.

Reverberation Chamber:

A device built to simulate room reflections.

Reverberation Envelope:

The attack, decay, sustain and release of the reverberation volume; or how fast the reverberation reaches peak level and its rate of decay.

RF Interference:

The unwanted noise introduced into electronics, circuits and/or audio systems by the presence of RF signals. RF interference in a system can result in humming, buzzing, static or even the reproduction of radio transmissions.

RF Signals (or RF):

Short for Radio Frequency Signals, electromagnetic waves that carry wireless radio and television signals. The vast majority of RF signals exist at frequencies higher than 100 kHz.

Rhythm Section:

The musical instruments in a band or ensemble that are responsible for playing rhythmic parts rather than melody parts. In contemporary music, rhythm sections typically consist of drums and bass, along with some combination of percussion, piano/keyboard and/or guitars.

Rhythm Track(s):

The recording of the rhythm instruments in a music production.

Ribbon Microphone:

A microphone that converts sound waves to electrical current via a thin conductive ribbon set between magnetic poles. Ribbon microphones are almost always responsive to sound on both sides of the ribbon, creating a bi-directional or figure-8 pattern.


A short melody repeatedly played in a tune often with variation between vocal lines.

Rise Time:

The rate at which an audio waveform makes a sudden increase to a higher amplitude.

RMS Meter:

A meter that recognizes and responds to the effective average, the RMS level, or the effective average value of an AC waveform, rather than to the peak level. (See also “Root-Mean-Square,” “Peak Meter.”)


The reduction of signal level as the frequency of the signal moves away from the cut-off frequency, especially when the cut-off rate is mild.

Room Equalization:

In live audio, an equalizer inserted in the monitor system that attempts to compensate for frequency response changes caused by room acoustics.

Room Sound:

The natural ambience of a room, including the reverberation and background noise.

Room Tone:

The natural background noise occurring in a room without music playing or people speaking. In recording audio for film and TV, on-set sound mixers capture a take of room tone for the purpose of providing continuity between clips of dialogue during post-production.

Root Mean Square (RMS):

The effective average value of an AC waveform. Used as a measure of the overall level of the sound rather than just measuring by the peaks. (See also “RMS Metering,” “Peak Metering.”)

Rotating Head:

A circular head with two (or more) gaps that rotates against the direction of tape motion at a slight angle to the tape travel.


A low-frequency noise, typically caused by earth/floor vibration or by uneven surfaces in the drive mechanism of a tape recorder or playback unit.


Abbreviation for “Sony/Phillips Digital Interface,” a protocol for sending and receiving digital audio signals using a common RCA connector.


A setting on an analog multitrack tape recorder that will prevent a track from recording when the record button is pressed.

Safety Take (ST):

An additional take of audio captured for good measure after a take of acceptable quality has been recorded.


1) In digital recording, the numerical measure of the level of a waveform at a given instant of time. Analog music is represented digitally by many samples taken in rapid succession. 2) A short segment of audio recorded for the purpose of reproducing and manipulating the sound digitally.

Sample Dump Standard (SDS):

See “MIDI Sample Dump Standard.”

Sample Rate:

In digital recording, the number of times per second that samples are taken. The higher the sample rate, the more realistic the digital reproduction of the sound, and the higher frequencies of the sound can be reproduced. In digital audio, the quality and resolution of a digitally reproduced sound are described as a combination of sample rate and bitrate. (See also “Bitrate.”)

Sample Rate Conversion:

The conversion of digital audio taken at one sample rate to a different sample rate without first converting the signal to analog.


A device that records and plays samples, often with features for editing, manipulating and storing the samples.


1) The point at which magnetic tape reaches full magnetization due to an excess of sound level. This creates some distortion that some audiophiles describe as “analog warmth” a desirable quality in certain instances. 2) The audio distortion that occurs by overdriving a signal through a tube amplifier or preamp—again producing color and warmth in the sound that engineers often find appealing. 3) A digital plugin that emulates tape or tube saturation.

Sawtooth Wave:

A waveform that jumps from a zero value to a peak value and then immediately drops to a zero value for each cycle. (Sometimes also called “Ramp Wave.”)


1) A descriptive term meaning “temporary”. 2) A scratch vocal is a vocal done during a basic recording session to help the musicians play their parts. At a later date the final vocal track is overdubbed. 3) The action of a musician or disc jockey quickly moving a record back and forth on a turntable reproducing the stylus motion to create a rhythm pattern of sound.


The action or function of shuttling a piece of recorded audio back and forth while monitoring it, typically to locate a certain point in the recording. In earlier days, scrubbing was done with reel-to-reel analog tape by manually turning the reels to pull the tape across the playhead. Today, scrubbing is primarily done digitally on a DAW by dragging the cursor back and forth across the waveform.

Second Engineer:

An assistant recording engineer.


See “Auxiliary Send.”

Send Level:

A control determining the signal level sent to a send bus.


1) In audio settings, describes the amount of output that a microphone can produce from a standard level of sound, as compared to the output of another microphone from the same sound level. 2) In music, describes the artistic persona in general.


1) A pre-programmed set of musical events, such as pitches, sounding of samples, and rests, to be played in order by a device. Also refers to the action of programming the device to play this set of musical events. 2) Loosely referring to a segment of music in general.


A computerized device or software that can be programmed to play a stepped order of musical events, including playing of pitches, sounding of samples, and rests.

Serial Data:

A digital data stream where individual bits are transmitted one after another over a single connection (as opposed to “parallel data,” in which multiple bits can be sent at once). Most data connections in the recording studio transmit serial data—for example, USB, Firewire and MIDI.

Series Connection:

Connecting devices (especially circuit elements) so that the electrical signal flows from one thing to the next, to the next, etc.

Set Up:

The positioning of microphones, instruments, connections and monitoring in the studio, as well as the controls and levels on consoles, DAWs, etc., in preparation for recording.


A frequency response of an equalization circuit where the boost or cut of frequencies forms a shelf on a frequency response graph. A high-frequency shelf control affects signal levels at the set frequency and all frequencies above it; a low-frequency shelf does the same for signals at and below the set frequency.

Shelf Filter:

A name for the circuit in an equalizer used to obtain the shelf.


The outer conductive wrapping around an inner wire or wires in a cable, for the purpose of shielding the cable from picking up external electromagnetic interference.

Shielded Cable:

Cable that has a shield around an inner conductor or inner conductors.

Shock Mount:

An elastic mount on microphone stand that reduces the impact of unwanted vibrations that may affect the stand (for example, floor vibrations from footsteps).

Short (Short Circuit):

A direct connection between two points in a circuit that (usually) should not be connected.

Short Delay:

Delay times under 20 milliseconds.

Shortest Path:

A technique in recording that routes the signal through the least amount of active (amplified) devices during recording.

Shotgun Microphone:

A microphone with a long line filter, a tube that acoustically cancels sound arriving from the side, to make the microphone pick up much better in one direction than in any other direction. This gives the shotgun mic a tight, hypercardioid pickup pattern. Shotgun microphones are commonly used to record dialogue in filming situations, usually held on a boom stand with a shock mount.


Energy from a voice centered around 7 kHz, caused by pronouncing “s”, “sh” or “ch” sounds.


An auxiliary input to a signal processor that allows control of the processing to be triggered by an external source. A common use of sidechaining is in compressors, particularly in ducking effects where the presence of a particular audio signal triggers the compression of another audio signal. (See also “Ducking.”)


1) In audio, an alternating current (or voltage) matching the waveform of, or being originally obtained from, a sound pressure wave. 2) Also in audio, an alternating current (or voltage) between 20 Hz and 20,000 Hz. 3) A digital audio bit stream.

Signal Flow:

1) In the general sense, the path that an audio signal travels from the sound source to the system output. (For example, from the vocalist’s voice into the microphone, through the cables, into the preamp, out of the preamp into the console, through all inserts and buses, and output into the DAW for recording.) 2) Signal flow is often specifically meant to refer to the routing of an audio signal through the console, from input to output.

Signal Processing:

The practice of altering the character or sound of an audio signal through a variety of devices or plug-ins, such as equalizers, compressors, reverb units, etc.

Signal-to-Noise Ratio (SNR):

The comparison of the strength of a signal level to the amount of noise emitted by the device, expressed in dB.

Sine Wave:

The waveform of a “pure tone”—a sound vibrating at a single frequency. Depicted graphically, a sine wave is a smooth, oscillating curve.

Slap Echo:

Also called Slapback) A single, distinct echo of a sound, which can result naturally from higher frequencies reflecting off a non-absorbent wall, or artificially reproduced by a signal processing unit or plugin. Slap echo creates a “live” sounding effect similar to what you would hear in an arena.

Slate (Slating):

1) In video/film, the identification of a scene and take at the beginning of the clip for the purpose of video editing. This is done by presenting the scene/take in written form in front of the camera on a clapboard, calling the scene/take verbally, then marking it audibly with the clapper for the purpose of syncing audio to the video. 2) In audio recording, the similar practice of identifying a take of music by an audible cue at the beginning of the recorded track. While some engineers still practice this, it was more necessary in the days of analog tape recording because it helped editors keep track of the location of takes on the recorder. Today, DAWs make it easier to keep track by identifying each take visually on the screen.


1) In audio, any device which syncs to another device by reading the clock information emitted by the master device. 2) In MIDI, any device or instrument that is being operated remotely by MIDI information sent from another device.

Smart FSK:

An updated form of Frequency-Shift Key (FSK) sync that enables MIDI devices to sync to analog tape recorders and/or other recording devices. A digital signal with MIDI Song Position Pointer (SPP) data is encoded onto a spare track, which identifies the exact bar, measure and beat for MIDI sequencers/devices at any point in the recording. This enables the device to start playing at exactly the right place and tempo no matter where you start the tape. (See also “Frequency-Shift Key.”)


1) Abbreviation for Society of Motion Picture and Television Engineers. 2) See “SMPTE Time Code.”

SMPTE Time Code:

(Abbreviated “SMPTE“) A standardized timing and sync signal protocol created by the Society of Motion Picture and Television Engineers for the purpose of syncing audio to video/film, which can also be used for syncing purposes in audio recording environments. Many audio professionals simply refer to this time code as “SMPTE.”


1) Abbreviation for “snare drum.” 2) The metal strands stretched across the bottom head of a snare drum, which help produce the piercing “cracking” sound when the snare drum is struck.

Sock Cymbal:

A rarely used alternate term for “hi-hat,” left over from the days when hi-hat cymbals were placed at “sock level.” (See also “Hi-Hat.”)

Soft Knee:

In compression, refers to the gradual introduction of compression of the signal once the sound level crosses the threshold. (See also “Knee.”)

Software Instrument:

See “Virtual Instrument.”


The action of making connections with solder, a soft metal alloy that is used to bond two metal surfaces by melting. In audio settings, soldering is used for a variety of purposes in building, modifying or repairing gear—perhaps most often to repair or build audio cables as a cost-saving effort, as opposed to buying new ones or sending them off for repair.

Solid State:

In electronics, refers to the use of transistors and semiconductors (solid materials) in the building of electronic devices, as opposed to tubes. In the recording studio, solid state amplifiers have different properties than tube amps, and each has its own advantages and disadvantages. A more recent application of solid state construction is in computer devices, particularly solid state hard drives (SSD), which transfer data more quickly than conventional spinning disc drives, and are less prone to breakage.


1) A circuit in a console or DAW that allows one or more selected channels to be heard or to reach the output, while other channels are automatically muted. 2) In music, a segment of a song in which a vocalist or instrument is featured above other instruments.

Solo Switch:

A switch that activates the solo function on a console or DAW.

Song Position Pointer (SPP):

A MIDI message that enables connected MIDI devices to locate a given point in the song. Used in conjunction with MIDI clock as a way of synchronizing devices or telling a connected device when to begin playing.

Sound Blanket:

A thick blanket that can be put on floors or hung to add sound absorption to the room, and help prevent sound reflections.

Sound Effects (SFX):

Sounds other than dialogue, narration or music that are added to audio, usually in the context of film/video.

Sound File:

A digital audio recording that can be stored in a computer or on a digital storage medium (such as a hard disk).

Sound Level:

See “Sound Pressure Level.”

Sound Module:

An electronic instrument (tone generator, synth or sampler playback unit) that has no playable interface, but instead responds to incoming MIDI message. Often sound modules were created as the “brains” of popular synthesizers, cheaper versions of the product that could be added to an existing MIDI configuration. Today, sound modules can also occur as software versions or plugins to be accessed on a computer.

Sound Pressure Level (SPL):

In scientific/technical terms, the measure of the change in air pressure caused by a sound wave, measured in dB. We hear and perceive SPL in terms of amplitude, volume or loudness of the sound.

Sound Source:

The origin of a sound, whose vibrations create sound waves.

Sound Wave:

(Also called “Sound Pressure Wave”) A wave caused by a vibration that results in slight variations in air pressure, which we hear as sound.


1) Broadly speaking, refers to any/all audio that accompanies an instance of visual media, whether music, dialogue or SFX. 2) In more common terms, refers to the musical score and/or licensed music synced to a film, video, TV program or video game.

Spaced Pair:

(Also called “A/B Technique“) A stereo microphone placement technique in which two cardioid or omnidirectional microphones are spaced somewhere between 3-10 feet apart from each other (depending on the size of the sound source) to create a left/right stereo image.


A device that converts electrical signals to sound; more technically, a transducer that changes an electrical audio signal into sound pressure waves.

Speed of Sound:

Generally speaking, the time it takes for a sound wave to travel through a medium. Sound travels at different speeds through solids, liquids and gases, and though we usually think of sound as traveling through the air, differences in temperature, air pressure and humidity can also affect how fast sound travels.  For a starting frame of reference, the speed of sound is generally defined by aerospace engineers as “Mach 1.0,” translating to 340.29 meters per second (approx. 761.1 mph, or 1116 feet per second), which is how fast sound travels through the air at sea level at a temperature of 15 degrees Celsius (59 degrees Fahrenheit). By contrast, at 70 degrees Fahrenheit under standard atmospheric conditions, the speed of sound is about 344 m/s, or 770 mph. (See how complicated it can get?)


See “Sound Pressure Level.”


Historically, the act of attaching previously cut pieces of audio tape or film in precise locations by applying a special kind of adhesive tape on the back. This is/was done for the purpose of shortening sections of audio or editing film. Today, splicing has become a very simple process by editing sections of audio or video digitally with a DAW or film editing software.

Spring Reverb:

A device that simulates reverberation by creating vibrations within a metal spring by attaching it to a transducer and sending the audio signal through it. A pickup at the other end converts those vibrations into an electrical signal which is mixed with the original audio signal. While the physical spring reverbs still exist, most studios emulate spring reverb with the use of plug-ins or hardware reverb units.

Square Wave:

A wave shape in which the voltage rises instantly to one level, stays at that level for a time, instantly falls to another level and stays at that level, and finally instantly rises to its original level to complete the wave cycle.


1) The partially enclosed or raised area where live musicians perform. 2) In reverberation effects devices, an echo added before the reverberation to simulate echoes that would come from a concert stage.

Stage Monitor:

A speaker on the stage that enables performers to hear themselves and to hear what the other musicians are playing on stage.

Standard Operating Level:

A reference voltage level or maximum average level that should not be exceeded in normal operation.

Standing Wave:

An unwanted sound wave pattern that often occurs when the sound wave bounces between two reflective parallel surfaces in a room, and the reflected waves interfere with the initial wave coming from the sound source, in which the combined wavelength of the affected frequency is effectively the length of the room. This creates the audible illusion that the wave is standing still, so the frequency is amplified to an unwanted level in certain parts of the room while nearly absent in others. Standing waves are most common in square or rectangular rooms with parallel surfaces, so acoustic designers try to prevent these waves by installing absorptive materials or introducing other items to offset the parallel surfaces.

Step Mode:

A setting in a sequencer or DAW in which notes are input manually, one note or step at a time.


A recording or reproduction of at least two channels where positioning of instrument sounds left to right can be perceived.

Stereo Image:

The audible perception of stereo, in which different sounds sources appear to be coming from far left, far right or any place in between.

Stereo Micing:

Placement of two or more mics so that their outputs combine to create a stereo image.


To put away equipment and clean up after a recording session.


Additional information bits that are recorded alongside digital audio, used for control and playback purposes.


A unit smaller than one frame in SMPTE time code.


A number of input channels on a console that can be controlled and adjusted as a single set before sending the combined signal to the master output. Sometimes also called “Submix,” “Bus” or just “Group.”


The fader which controls the combined level of sound from several channels during mixdown or recording.


See “Subgroup.”

Subtractive Synthesis:

An old-school method of sound synthesis in which sounds are designed and created by generating harmonically rich waveforms, then filtering out unwanted harmonics to arrive at the desired sound.


A signal that is the mix of the two stereo channels at equal level and in phase.


The process of blending two or more signals into one mixed signal. In summing audio, each successive channel adds volume to the overall signal, so channels must be mixed in order to prevent peaking the combined signal.

Super-Cardioid Pattern:

A very tight cardioid microphone pattern with maximum sensitivity on axis and the least amount of sensitivity approximately 150 degrees off-axis.

Surround Sound:

A technique of recording and playback in which the listener hears various aspects of the sound from front to back as well as side-to-side—a 360-degree audio image, as opposed to the standard stereo left-right image. Surround sound can occur in various formats with different numbers of speakers arrayed through the room. Surround sound today is most commonly used in film and TV production.


The third of the four stages of a sound (Attack, Decay, Sustain and Release, or the ADSR envelope), the sustain is the part of the sound that holds at approximately the same volume after the initial attack and drop in volume level (decay), until the sound stops playing. In some instruments, sustain is short or virtually nonexistent; in many instruments, sustain loses volume over time until the sound dies off (for example, in a held piano note). In synthesizers and samplers, the sustain function can be set to hold the note at the same volume level indefinitely until the key is released.


A vague term referring to the fine-tuning of audio in the post-production stage of recording. Effectively, any small “tweaks” to to make the audio sound better is considered sweetening.


A device that makes and/or breaks electrical connections.

Switchable Pattern Microphone:

A microphone having the capability of two or more pickup patterns, which can be toggled by use of a switch on the microphone.


Short for “Synchronization.” In audio/studio settings, sync refers to the correlating of two or more pieces of audio or video in relation to each other. This can include syncing two recording/playback devices timed to a sync signal like SMPTE Time Code, synchronizing audio with video in film or TV, and many other examples. Licensing a song or piece of music for placement in film, TV or video is also referred to as “syncing.”

Sync Pop:

A short tone (usually a sine wave at 1 kHz, and the length of a frame of film) that is placed exactly two seconds before the start of a piece of film or music. The sync pop is used to make sure that all related audio and video tracks stay in sync with each other through all stages of post-production.


A musical instrument that uses electrical oscillators to generate tones artificially, either to simulate the sounds of other instruments or to create other sounds not possible with other instruments.

System Exclusive (SysEx):

A MIDI message that will only be recognized by a unit of a particular manufacturer.


In analog tape recording, a device on the recorder that measures and regulates tape speed by emitting pulses as the tape moves across the head.

Tails Out:

A method of winding audio tape so that the end of the last recorded selection is at the outside of the reel.


The recording that is done between one start and stop of a tape recorder or DAW.

Take Notation:

Writing down the takes of the tune being recorded on a take sheet or on the track log with comments. Take notation was/is recommended for analog tape recording, but in most studios, this function is now accomplished on the DAW.

Talk Box:

An effects unit that enables a musician to modulate the sound of his/her instrument via a tube placed into the mouth. Historically, talk boxes have been used as an effect for guitars, but they can be used to modify other instruments, as well.


A microphone in the control room carried on a separate circuit from the recorded channels, allowing the engineer to communicate with the musicians in the live room or sound booths through the monitoring system.

Tape Delay:

A signal processing technique for creating artificial delay or echoes by manipulating time delays with analog tape machines. This technique began by routing the signal to a separate tape recorder and mixing the delayed response back in with the signal; it then evolved to the use of dedicated machines that could adjust the length of the delay by adjusting the distance between the record and playback heads. Today, most tape delay effects in the studio are simulated digitally through plug-ins in a DAW.

Tape Guide:

Any stationary or rotating device which directs the tape past the heads on a tape machine, or from one reel to the other.

Tape Hiss:

The natural high-frequency noise that occurs on analog tape due to the magnetic particles from which the tape is made. Tape hiss constitutes most of the noise floor that occurs in analog recording, and can be reduced by using tape constructed of finer magnetic particles. (See also “Noise Floor.”)

Tape Loop:

A length of tape with the ends spliced together so that the recording will play continuously.

Tape Recording Equalization:

The increase in amplitude of signals, in a tape machine’s electronics, at the high frequencies as a tape is recorded to keep high-frequency signals recorded above the tape hiss.

Telephone Filter:

A filter used to simulate the audio heard through a telephone receiver by removing signals at frequencies below 300 Hz and above 3500 Hz.


The rate at which the music moves, measured in Beats Per Minute (BPM).

Tempo Mapping:

The act of programming a sequencer or DAW to follow the tempo variations of a recorded performance. Unlike beat mapping or beatmatching, both of which effectively adjust the recording to fit a set tempo, tempo mapping adjusts the tempo of the project (especially the MIDI instruments) to match the natural tempo nuances of the recorded material. (See also “Beat Mapping,” “Beatmatching.”)


1) A point of connection between two wires, including the plug on the end of a cable, and the jack on a piece of equipment. 2) Refers to the keyboard and monitor of a computer that enable the user to enter information and to access data.

Test Oscillator:

A device that generates audio waveforms at various frequencies for testing purposes.

Test Pressing:

One of a few initial vinyl record copies pressed from the first stamper made, which is listened to and visually inspected to approve the quality before more copies are pressed.

Test Tones:

1) A recording of several single-frequency tones at the beginning of a tape reel at the magnetic reference level that will be used to record the program.  2) Artificially generated tones that are used to calibrate an audio system.


See “Total Harmonic Distortion.”

Thin Sound:

A vague term describing an audio signal that that is lacking in certain frequencies, especially on the low end. Over-filtering a signal with an EQ can produce a thin sound, for example.

Three-To-One Rule:

A principle of microphone placement that says when multiple mics are used at once, the distance between microphones should be at least three times the distance between each microphone and its respective sound source. The three-to-one rule is used to prevent phasing issues between the audio signals.

Three-Way Speaker:

A speaker system that has separate speakers to reproduce the bass, mid-range and treble frequencies.


The level at which a dynamics processing unit will begin to change the gain of the incoming signal.

Threshold of Hearing:

Described as the sound pressure level at which people can hear only 50 percent of the time.


In a speaker, the small opening in a horn or in a driver through which the sound wave passes from the driver to the horn.


1) In speakers and in microphones, describes the amount of unrestricted movement that the diaphragm can make. In microphone, this affects the mic’s sensitivity; in speakers, it affects the distance of sound projection. (A speaker designed for smaller spaces has a “short throw,” while one designed for a farther projection has a “long throw.” 2) In speakers, “throw” may also be used to describe the speaker’s directional output, often based on the frequencies it emits. A horn, for example, emits high frequencies in a limited angle of direction, so it has a “long throw,” while a subwoofer emits low frequencies in all directions and has a “short throw.” 3) Something a producer, engineer or musician might do with whatever is in his/her hand during a moment of intense frustration.

Tie Lines:

Cables with connectors at both ends, which are usually run through walls or floors in the studio, for the purpose of sending signals between rooms. Tie lines provide a great semi-permanent way to route and configure signal paths quickly through various parts of the studio and help the engineer keep track of signal flow.


The sound quality that makes one instrument sound different from other instruments, even while playing the same pitch. The timbre of a trumpet, for example, is what makes it sound like a trumpet and not like a flute. Timbre is largely shaped through the presence, absence and complexity of harmonics when the instrument is played.

Time Code:

A standardized timing signal used to help devices sync with one another, or to sync audio to video. Common time codes used in the studio are MIDI Time Code (MTC) and SMPTE time code.

Time Compression/Expansion:

(Also called “Time Stretching” or “Time Shifting“) The process of speeding up or slowing down an audio recording without changing the pitch of the sounds.

Time Constant:

A complex mathematical ides that basically describes the time delay between when an electrical voltage is applied to a circuit and when the circuit responds to it.


The small drums (as little as 10 inch diameter) that mount on racks above the kick drum and the large drums in a drum set.


1) Any single-frequency signal or sound.  2) The sound quality of an instrument’s sound relative to the amount of energy present at different frequencies.

Tone Generator:

1) A device that puts out test tones at various frequencies to align a tape machine or for other testing purposes. 2) The circuits in a synthesizer that create the audio signals put out by the unit, usually to emulate the sound of another instrument.


The technique of controlling the start of a note in a brass or woodwind instrument with the tongue.

Total Harmonic Distortion (THD):

The measure of the difference between the level of harmonic frequencies at the output stage of an amplifier as compared with the input stage, a ratio expressed as a percentage. It’s a fine-tuning specification barely perceptible to many ears, but the lower the THD, the more accurately the amplifier/speaker is reproducing the sound.

Touch Sensitive:

See “Velocity Sensitive.”


1) One audio recording made on a portion of the width of a multitrack tape, or created as a digital representation using a DAW. 2) 2) One set of control commands in a sequencer or DAW that is used to control one instrument over one MIDI channel. 3) See “Band Track.”

Track Log/Track Assignment Sheet:

A sheet of paper kept with a multitrack tape which tells which instrument was recorded on each track.


The act of recording the individual tracks of a multitrack recording.


A device that converts energy from one medium to another. Transducers are prevalent throughout the equipment in a recording studio.


The initial high-energy peak at the beginning of a waveform, such as one caused by the percussive action of a pick or hammer hitting a string, or the strike of a drum.


1) The portion of a tape machine that moves the tape from the supply reel, past the heads, to the take-up reel. 2) The set of controls found on a DAW or sequencer for starting, stopping pausing, fast-forward and rewind, emulating the functions of a tape machine transport.


To shift a set of musical notes by a fixed interval. This can happen in a number of ways—for example: 1) by rewriting an entire piece of music in a new key; 2) by shifting the tuning of an instrument so that it plays at a lower or higher interval than the note played (either artificially, as with an electronic keyboard, or by the natural tuning of a transposed instrument, like a trumpet); or 3) Transposing on-the-fly, playing at a set interval above or below what is written (also known as transposing by sight).


1) A filter designed to reject audio signals at certain frequencies. 2) An object designed with acoustically absorptive material, placed into walls to reduce low frequency reflections in the room (also called “bass trap”). 3) Another word for a drum set (as in “trap set”).


A wavering or “shaking” musical effect, created either by quick reiterations of the notes (as in a violin tremolo) or by rapid shifts in amplitude.

Triangular Wave:

A harmonically rich waveform that appears triangular in shape when depicted graphically, due to a combination of the presence of odd harmonics and rapid rolloff.


The signal or the action of sending a signal to control the start of an event.

Trim/Trim Control:

A device that reduces or increases the signal strength in an amplifier, often over a restricted range. Often used interchangeably with gain, but usually referring to fine-tuning signal strength, rather than merely amplifying it.


1) The shortening of an audio signal, sample or song, typically by cutting off the end. 2) The dropping of bits of data when the bit resolution is reduced (for example, from 24-bit to 16-bit), causing digital distortion unless dithering is applied.

Tuning Fork:

A metal fork with two prongs that vibrate with a fairly pure tone of one frequency when the fork is struck.


A device to support and rotate a phonograph record during playback.


A speaker designed to reproduce only the higher frequencies of the sound.

Two-Way Speaker:

A speaker system with separate speakers to reproduce the lower frequencies (woofer) and the higher frequencies (tweeter).

Unbalanced Cable:

A cable with two conductors (a signal wire and a ground wire) and connectors on each end. Unbalanced cables are often susceptible to electromagnetic interference and noise. Examples of unbalanced cables are guitar/instrument cables (also called tip-sleeve or TS cables) and RCA cables.

Unidirectional Pattern:

A microphone pick-up pattern which is more sensitive to sound arriving from one direction than from any other.


Several performers, instruments or sound sources that are sounding at the same time and with the same pitch.

Unity Gain:

The scenario in which there is no increase or decrease in signal strength at the output of an amplifier or device compared to the signal strength at the input (typically described as 0 dB).

Vacuum Tube:

A diode, a glass tube with the gases removed, through which electrical current can flow. In audio, vacuum tubes are used in amplifiers, oscillators, and other analog devices.


A part of a song or chord progression that is repeated, usually at the end of the song, and usually the chorus or part of the chorus.

Vamp and Fade:

A method of ending the recording of a song where the music has a repeating part and the engineer reduces volume until the music fades out.


A control on a tape machine that changes the play speed.


Shorthand for “Voltage Controlled Amplifier,” an amp whose gain is affected by an external voltage fed to it.

VCA Automation:

A system of mix automation in some mixing consoles in which sound levels or other functions are altered through the use of voltage controlled amplifiers.

VCA Group:

Several VCA faders that are fed control voltages from a group master slide. A feature in higher-end mixing boards that enables the engineer to control groupings of independent signals by a single fader that uses VCA to adjust the voltage sent to each channel.


See “Voltage Controlled Oscillator.”

Velocity Message:

In synthesizers and keyboard controllers, a MIDI message that transmits data on how hard the key was struck. Velocity messages can be used to transmit volume information, as well as triggering different samples on a multi-sampled instrument patch.

Velocity Microphone:

See “Pressure-Gradient Microphone.”

Velocity Sensitive:

(Also called “Touch Sensitive“) A feature on a MIDI instrument such as a keyboard that transmits a MIDI velocity message depending on how hard the key is struck.


A smooth and repeated changing of the pitch up and down from the regular musical pitch, often done by singers or performed by string and wind players.

Virtual Instrument:

(Also called Software Instrument) One of a number of software-based synthesizers, samplers or sound samples that are stored and accessed via computer and performed by an external MIDI controller, rather than in a standalone synthesizer or module. Because of the wide versatility available from these instruments, a growing number of composers and electronic musicians are working with virtual instruments that can be stored in hard drives, rather than purchasing stacks of keyboards and modules.

Vocal Booth:

A room in the recording studio that is used for recording vocals in isolation. This practice prevents bleed-through of the sounds of other instruments into the vocal microphone, and also reduces natural ambience and reverberation in the vocal recording.


An audio processing device effects device or plug-in that analyzes the characteristics of an audio signal and uses them to affect another synthesized signal. Primarily developed for the purpose of producing synthesized voice effects from human speech, a vocoder creates the characteristic robotic vocal sound or the “human synthesizer” effect that makes it sound like the synth is speaking or singing words.


1) Besides the obvious definition of the sound humans make from their mouths…in synthesizers, a voice refers to one of a number of sounds/pitches that may be played at the same time. “Monophonic” means only one voice plays at a time, while “polyphonic” means multiple voices can sound at once. (See also “Polyphonic”, “Monophonic.”) 2) In some synthesizers, like Yamaha, “voice” may also refer to a specific sound patch available on the synth.

Voice Over:

The recording of vocal announcements or narration over a bed of music in video, film or commercials.

Volatile Memory:

Computer memory whose data will will be lost when the computer is turned off. RAM (Random Access Memory) is the most common form of volatile memory.


The difference in electrical force or pressure (“potential”) between two objects, causing a flow of electric current between them.

Voltage Controlled Amplifier (VCA):

An amplifier whose gain level is affected by an external voltage being sent to it. VCAs are commonly used in synthesizers, signal processors, and as a means of automation for some mixing consoles.

Voltage Controlled Filter:

A filter (especially a low-pass filter) that will change its cutoff frequency according to a control voltage fed to its control input.

Voltage Controlled Oscillator (VCO):

An oscillator whose frequencies are modified by voltage input. Most commonly found in synthesizers.


A common, non-technical term that either refers to sound pressure level (which we hear as loudness), or to audio voltage level.

Volume Unit (VU):

A unit to measure perceived loudness changes in audio. The unit is basically the decibel change of the average level as read by a VU Meter. (See also “VU Meter.”)


A Latin word meaning “voice,” often used as an abbreviation for track logs in the studio.

VU Meter:

A meter that reads audio voltage levels in or out of a piece of equipment and is designed to match the ear’s response to sudden changes in level.


Unit of electrical power.


A visual representation or graphic of a sound wave, audio signal or other type of wave, showing the wave’s oscillations above and below the zero line.


The physical length of one cycle of a wave, measured in feet, inches, etc. The longer the wavelength of a sound wave, the lower its frequency; the shorter the wavelength, the higher the frequency.


An equalization curve used in audio tests that compensates for the Fletcher Munson Curve at various levels. (See also “Fletcher-Munson Curves.”)


Refers to a signal that has the full amount of an effect (like reverb) applied to it, as opposed to “dry,” which refers to the un-effected sound. Many times, the preferred sound in mixing will be a blend of wet and dry signals. (See also “Dry.”)

White Noise:

A noise signal containing an equal spread of energy across all audible frequencies. Like pink noise, engineers often send a white noise signal through audio equipment for tuning and calibration purposes, or in EQ-ing a live audio space. (See also “Pink Noise.”)

Whole Step:

A change in pitch equivalent to two half steps, or the difference in pitch between two piano keys.

Wild Sound:

In film and video, audio that is recorded separately from the visual that may be added to the audio track later, and does not need to be synchronized with the picture.

Wind Controller:

A device that is played like a wind instrument to control a synthesizer, module or virtual instrument via MIDI signals, as opposed to a keyboard controller.


A covering that fits over a microphone to reduce the excessive noise resulting from wind blowing into the mic. Typically used for recording in outdoor locations.

Wireless Microphone:

A microphone that transmits its signal over an FM frequency to a receiver offstage, rather than traveling over an audio cable.


A speaker that is designed to reproduce bass frequencies only.

Write Mode:

A mode of operation in an automated console where the engineer is in control of channel gain and the computer is recording the gain changes over time.

XLR Cable:

A balanced microphone cable utilizing XLR connectors. (See also “XLR Connector.”)

XLR Connector:

A balanced cable connector consisting of 3 or 7 pins, most commonly used in microphone cables.

XY Miking:

A coincident stereo microphone placement technique in which two cardioid microphones are placed with their heads toward each other at a 90-degree angle, and as close together as possible. (See also “Coincident Miking.”)


A cable with three connectors so that one output may be sent to two inputs.  Basically, a signal splitter done with spliced wires rather than components.


In analog tape recording, refers to the tilt of the tape head in the direction perpendicular to the tape travel.

Zero-Order Hold (ZOH):

Refers to the mathematical expression of the signal processing done by a conventional digital-to-analog converter (DAC).