When an analogue signal is sampled for conversion into a digital data stream, the sampling frequency must be at least twice that of the highest frequency component of the input signal. If this rule is disobeyed, the sampling process becomes ambiguous as there are insufficient points to define each cycle of the waveform. This resulting in unwanted anharmonic distortion component frequencies (not musically related) being added to the wanted signal.

A sequence of instructions describing how to perform a specific task. Algorithms are often implemented in a computer language and compiled into a computer program. In the context of effects units, algorithms usually describe a software building block designed to create a specific effect or combination of effects.

A means of generating a control signal in a synthesizer based on how much pressure is applied to the keys of a MIDI keyboard. Most instruments that support this do not have independent pressure sensing for all keys ('polyphonic aftertouch'), but rather detect the overall pressure by means of a sensing strip running beneath the keys. Aftertouch is typically used to control such functions as vibrato depth, filter brightness, loudness and so on.

A system used within mixing consoles to allow specific signals to be monitored at the level set by their fader, typically after the pan-pot for channel AFL. Aux sends, matrix outputs and so forth are generally monitored AFL rather than Pre Fade Listen (see PFL and Solo).

An AES standard which defines the connectivity, powering, remote control and audio format of ‘digital microphones’. The audio information is conveyed as AES3 data, while a bespoke 10V phantom power supply conveys remote control and clocking information through an ingenious modulation technique.

An AES standard that defines a method of evaluating the dynamic range performance of analogue-to-digital (A-D) and digital-to-analogue (D-A) converters.

An AES standard that defines the use of a specific form of AES3 signal purely for clocking purposes. Also known as DARS (Digital Audio Reference Signal).

An AES standard which defines the serial MADI interface (Multichannel Audio Digital Interface). MADi can convey either 56 or 64 channels via single coaxial or optical connections at base sample rates. A double-rate format with half the channel count is also available.

Acronym for Alesis Digital Audio Tape, referring to the company's popular range of digital eight-track tape machines released in the early 1990s. Now more commonly used as a shorthand term for the ADAT Lightpipe digital connection format.

A digital audio interface which passes two digital audio channels, plus embedded clocking, control and status data, with up to 24 bits per audio sample and supporting sample rates up to 384kHz.