A system used to reduce the amount of data needed to represent some information, such as an audio signal. Lossless audio data reduction systems, (eg. FLAC and ALAC) can fully and precisely reconstruct the original audio data with bit-accuracy, but the amount of data reduction is rarely much more than 2:1. Lossy data audio reduction systems (eg. MPEG, AAC, AC3 and others) permanently discard audio information that is deemed to have been 'masked' by more prominent sounds. The original data can never be retrieved, but the reduction in total data can be considerable (12:1 is common).

To reduce the signal amplitude or level. Normally specified in terms of (negative) decibels.

The time taken for a sound to achieve its maximum amplitude, or for an electronic device to reach the full extent of its action. Drums generally have a fast attack, whereas bowed strings typically have a slow attack. In compressors and gates, the attack time equates to how quickly the processor can reduce the signal level.

Acronymn for American Standard Code for Information Interchange (pronounced 'askey'). An internationally recognised code used to represent computer keyboard characters.

A device (or software) that allows a synthesizer or MIDI instrument to sequence around any notes currently being played. Most arpeggiators also allow the sound to be sequenced over several octaves, so that holding down a simple chord can result in an impressive repeating sequence of notes.

Arming a track or channel on a recording device places it in a condition where it is ready to record audio when the system is placed in record mode. Unarmed tracks won’t record audio even if the system is in record mode. When a track is armed the system monitoring usually auditions the input signal throughout the recording, whereas unarmed tracks usually replay any previously recorded audio.

Alternative term for a computer program.

A very steep low-pass filter used to limit the frequency range of an analogue signal prior to A/D conversion, so that the maximum frequency does not exceed half the sampling rate. (See A-D Conversion)

A system for synthesizing sounds by means of analogue circuitry, usually by filtering simple repeating waveforms.

The origin of the term is that the electrical audio signal inside a piece of equipment can be thought of as being ‘analogous’ to the original acoustic signal. Analogue circuitry uses a continually changing voltage or current to represent the audio signal. (cf. Digital)