Describes an unwanted short term corruption of a signal, or the unexplained, short term malfunction of a piece of equipment.

A universally agreed subset of the MIDI standard, created to enable manufacturers to build synthesizers, synth modules and plug-in instruments that exhibit an agreed minimum degree of compatibility.

An electronic device (analogue or digital) designed to mute low level signals so as to improve noise performance during pauses in the wanted material. (See also 'Expander'.)

A synthesizer control signal generated whenever a key is depressed on an electronic keyboard and used to trigger envelope generators and other events that need to be synchronised to key action.

Electrical isolation between two circuits. A transformer provides galvanic isolation because there is no direct electrical connection between the primary and secondary windings; the audio signal is passed via magnetic coupling. An opto-coupler also provides galvanic isolation, as the signal is passed via light modulation.

The act of optimising the signal level through each audio device in a signal chain, or through each section of a mixing console, to maintain an appropriate amount of headroom and keep the signal well above the system noise floor.

A subjective term used to describe sound, where the bass and low-mid frequencies have depth and where the high frequencies are smooth-sounding rather than being aggressive or fatiguing. Warm-sounding tube (valve) equipment may also exhibit some of the aspects of compression.

Unit of electrical power named after its founder, James Watt.

A guitar effects device where a bandpass filter is varied in frequency by means of a pedal control.

A specific way of mounting two directional microphone capsules such that they both receive sound waves from any direction at exactly the same time. Information about the direction of a sound source is captured in the form of level differences between the two capsule outputs. Commonly, the two microphones in an X-Y array are mounted with a mutual angle of 90 degrees, although other angles are sometimes used. The two capsules will have the same polar pattern, the choice of which determines the stereo recording angle (SRA). The X-Y configuration is entirely mono-compatible because there are no timing differences between the two channels.