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Welcome to Sound On Sound's indispensible, regularly updated, explanations of technical terms from the fields of Recording, Audio Production, Music Technology, MIDI, Music Software, Audio Plug-ins, Mac and PC Computing, Live Sound, Acoustics, Electronics and more...

If we do not explain a particular term below, please email and we will add it to our next update.

Last updated: 15/09/20

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Contact Cleaner

A compound designed to increase the conductivity of electrical contacts such as plugs, sockets and edge connectors. (cf. De-Oxidising Compound)

Continuous Controller (CC)

Type of MIDI message used to translate continuous parameter changes, such as from a pedal, wheel or breath control device.

Control Voltage

A variable voltage signal typically used to control the pitch of an oscillator or filter frequency in an analogue synthesizer. Most analogue synthesizers follow a one volt per octave convention, though there are exceptions. To use a pre-MIDI analogue synthesizer under MIDI control, a MIDI to CV converter is required.


A device which transcodes audio signals between the analogue and digital domains. An analogue-to-digital (A-D) converter accepts an analogue signal and converts it to a digital format, while a digital-to-analogue (D-A) converter does the reverse. The sample rate and wordlength of the digital format is often adjustable, as is the relative amplitude of analogue signal for a given digital level.


A mathematical process whereby the characteristics of one function (or signal) are imposed upon a second function (signal) , to produce a third function which combines both of their characteristics. (See Convolution Reverb). This process is performed in the digital domain by multiplying each individual sample value of a source signal with the impulse response of the wanted effect signal, so that the characteristics of the latter are imposed on the former.

Convolution Reverb

A computationally demanding, but very accurate method, of creating artificial reverberation derived from real acoustic spaces with all their natural complexity. In essence, a reverberant space is measured to obtain its unique impulse response. That impulse response is then convolved with a 'dry' (reverberant-free) source signal to create an output signal which contains the original (dry) source signal with the desired room's reverberation characteristics imposed upon it. The convolution process is performed in the digital domain and involves multiplying each individual sample of the source signal with the impulse response of the convolving signal. The same technique can be employed to impose the characteristics of any other audio signal processing or signal-shaping device onto a source signal, such as the characteristics of legacy equalisers, compressors, tape recorders and so forth.

Copy Protection

A method used by software manufacturers to prevent unauthorised copying.


Central Processing Unit - the number-crunching heart of a computer or other data processor.


Slang term relating to malfunction of computer program.


A set of audio filters designed to restrict and control the range of input signal frequencies which are passed to each loudspeaker drive unit. A typical two-way speaker will employ three filters: a high-pass filter allowing only the higher frequencies to feed the tweeter, a low pass filter that allows only the lower frequencies to feed the woofer, and a second high-pass filter that prevents subsonic signals from damaging the woofer.

Crossover frequency

The frequency at which one driver ceases to produce most of the sound and a second driver takes over. In the case of a two-way speaker the crossover frequency is usually between 1 and 3kHz.

Cut and Paste Editing

The ability to copy or move sections of a recording to new locations.

Cut-off Frequency

The frequency above or below which attenuation begins in a filter circuit.


see Control Voltage


One complete vibration (from maximum peak, through the negative peak, and back to the maximum again) of a sound source or its electrical equivalent. One cycle per second is expressed as 1 Hertz (Hz).