ANALOG-TO-DIGITAL (A/D) CONVERTER: A circuit that converts an analog audio signal into a stream of digital data (bit stream)

CHORUS: The main portion of a song that is repeated several times throughout the song with the same lyrics

COMPRESSION: The reduction in dynamic range or gain

COMPRESSION RATIO (SLOPE): In a compressor, the ratio of the change in input level (in dB) to the change in output level (in dB). For example, a 2:1 ratio means that for every 2 dB change ininput level, the output level changes 1 dB

COMPRESSOR: A signal processor that reduces dynamic range or gainby means of automatic volume control. An amplifier whose gain decreases as the input signal level increases above a preset point

DE-ESSER: A signal processor that removes excessive sibilance ("s" and "sh" sounds) by compressing high frequencies around 5 to 10 kHz

DI: Short for direct injection, recording with a direct box

DIGITAL AUDIO WORKSTATION (DAW): A computer, sound card, and editing software that allows you to record, edit and mix audio programs entirely in digital form. Stand-alone DAWs include real mixer controls; computer DAWS have virtual controls on-screen

DIGITAL-TO-ANALOG CONVERTER: A circuit that converts a digitalaudio signal into an analog audio signal

DIRECT BOX: A device used for connecting an amplified instrument directly to a mixer mic input. The direct box converts a high-impedance unbalanced audio signal into a low-impedance balanced audio signal

DIRECT INJECTION (DI): Recording with a direct box

DISTORTION: An unwanted change in the audio waveform, causing a raspy or gritty sound quality. The appearance of frequencies in a device's output signal that were not in the input signal. Distortion is caused by recording at too high a level, improper mixer settings, components failing, or vacuum tubes distorting. (Distortion can be desirable--for an electric guitar, for example.)

EQUALIZATION (EQ): The adjustment of frequency response to alter the tonal balance or to attenuate unwanted frequencies

EQUALIZER: A circuit that alters the frequency spectrum of a signal passed through it

EXPANDER: 1. A signal processor that increases the dynamic range of a signal passed through it. 2. An amplifer whose gain decreases as its input level decreases. When used as a noise gate, an expander reduces the gain of low-level signals to reduce noise between notes

FILTER: A circuit that sharply attenuates frequencies above or below a certain frequency. Used to reduce noise and leakage above or below the frequency range of an instrument or voice

FREQUENCY: The number of cycles per second of a sound wave or an audio signal, measured in hertz (Hz). A low frequency (for example, 100 Hz) has a low pitch; a high frequency (for example, 10,000 Hz) has a high pitch

HIGH PASS FILTER: A filter that passes frequencies above a certain frequency and attenuates frequencies below that same frequency. A low-cut filter

LOW PASS FILTER: A filter that passes frequencies below a certain frequency and attenuates frequencies above that same frequency. A high-cut filter

LIMITER: A signal processor whose output is constant above a preset input level. A compressor with a compression ratio of 10:1or greater, with the threshold set just below the point of distortion of the following device. Used to prevent distortion of attack transients or peaks

MONITOR: A loudspeaker in a control room

MONO-COMPATIBLE: A characteristic of a stereo program, in which the program channels can be combined to a mono program without altering the frequency response or balance. A mono-compatible stereo program has the same frequency response in stereo or mono because there is no delay or phase shift between channels to cause phase interference

NOISE GATE: A gate used to reduce or eliminate noise between notes

NON-DESTRUCTIVE EDITING: In a digital audio workstation, editing done by changing pointers (location markers) to information on the hard disk. A non-destructive edit can be undone

PARAMETRIC EQUALIZER: An equalizer with continuously variable parameters, such as frequency, bandwidth, and amount of boost or cut

PLUG-IN: Software effects that you install in your computer. The plug-in software becomes part of another program you are using, such as a digital editing program

POP FILTER: A screen placed on a microphone grille that attenuates or filters out pop disturbances before they strike the microphone diaphragm. Usually made of open-cell plastic foam or silk, a pop filter reduces pop and wind noise

PREAMPLIFIER (PREAMP): In an audio system, the first stage of amplification that boosts a mic-level signal to line level. A preamp is a stand-alone device or a circuit in a mixer

PREPRODUCTION: Planning in advance what you're going to do at a recording session, in terms of track assignments, overdubbing, studio layout, and microphone selection

PRODUCTION: The supervision of a recording session to create a satisfactory recording. This involves getting musicians together for the session, making musical suggestions to the musicians to enhance their performance, making suggestions to the engineer for sound balance and effects, and assisting with filling out any necessary paperwork (union, PRO, talent releases, assignments, copyright forms, etc.)

RELEASE TIME: In a compressor, the time it takes for the gain to return to normal after the end of a loud passage

SCRATCH VOCAL: A vocal performance that is done simultaneously with the rhythm instruments so that the musicians can keep their place in the song and get a feel for the song. Because it contains leakage, the scratch-vocal recording is usually erased. Then the singer overdubs the vocal part that is to be used in the final recording

SHELVING EQUALIZER: An equalizer that applies a constant boost or cut above or below a certain frequency, so that the shape of the frequency response resembles a shelf

SIBILANCE: In speech recording, excessive frequency components in the 5 to 10 kHz range, which are heard as an overemphasis of "s" and "sh" sounds

SOUND CARD: A circuit card that plugs into a computer, and converts an audio signal into computer data for storage in memory or on hard disk. The sound card also converts computer data into an audio signal

SOUND MODULE (SOUND GENERATOR): A synthesizer without a keyboard, containing several different timbres or voices. These sounds are triggered or played by MIDI signals from a sequencer program, or by a MIDI controller

TAKE: A recorded performance of a song. Usually, several takes are done of the same song, and the best one--or the best parts of several--become the final product

THRESHOLD: In a compressor or limiter, the input level above which compression or limiting takes place. In an expander, the input level below which expansion takes place