The characteristic of a filter that allows it to selectively pass a narrow range of frequencies. See Q.

Opposition to the flow of electrical current. Measured in Ohms.

The time taken for a signal level or processor gain to return to normal. Often used to describe the rate at which a synthesized sound reduces in level after a key has been released. Also used to describe the time taken for a compressor top restore unity gain after a signal has fallen below the threshold. Also known as ‘recovery time .‘

The way in which sound waves bounce off surfaces.

A term used to imply a standard audio CD. The name comes from the fact that the original specifications documents for the audio CD created by Sony and Philips had a red cover! Recordable CD-Rs are described as 'orange book' for similar reasons.

An audio process that can be carried out as the signal is being recorded or played back. The opposite is off-line, where the signal is processed in non-real time.

A digital tape machine using a rotating head system and a tape cassette.

An abbreviation for Random Access Memory. This is a type of memory used by computers for the temporary storage of programs and data, and all data is lost when the power is turned off. For that reason, work needs to be saved to disk if it is not to be lost.

A standard equipment (height) sizing format allowing products to be mounted between vertical rails in standardised 19-inch equipment racks.

A means of moving notes recorded in a MIDI sequencer so that they line up with user defined subdivisions of a musical bar, for example, 16s. The facility may be used to correct timing errors, but over-quantization can remove the human feel from a performance.