An early recording technique pioneered by Les Paul and others which was a simple form of overdubbing to build up a mix of sources. Also, the world's best recording technology magazine (see www.soundonsound.com).

A dedicated interface to transfer audio signals in and out of a computer. A Sound Card can be installed internally, or connected externally via USB2 or FireWire, and they are available in a wide range of formats, accommodating multiple analogue or digital audio signals (or both) in and out, as well as MIDI data in and out.

A term used to describe a cable used to carry multiple individual audio signals, typically between a stage and mixing console in live sound applications.

Sample Multiplexing (see ADAT ).

The Society of Motion Picture and Television Engineers (www.smpte.org) an American standards body. The term is also used to refer to a form of time code developed for the film industry but now extensively used in music and recording. SMPTE is a real-time digital code describing hours, minutes, seconds and film or video frames. Usually conveyed as an audible warble.

see Switching Power Supply

A device under the control of a master device. Often used to refer to synchronised recorders, or digital clocking devices.

The term 'slate' comes from the silent film practice of writing the scene, take and shot numbers with chalk on a slate and holding it up in front of the camera before the action starts, so that the film editor can identify the material. A role now replaced by the 'clapper-board' which adds an audio synchronisation marking facility as well. In an audio context, a slate is a verbal identification recorded just before each take to help identify it subsequently. This is normally achieved by using a talkback microphone routed to the main, group and/or direct outputs of a mixer. The console slate function often mixed a low frequency tone in with the microphone signal to help make locating the start of each take much easier when fast-winding the tape against the playback head. Each slate ident would be heard as a short, steady mid-frequency tone.

A device for removing or attenuating the noise component of a recording or transmission system without pre-conditioning the signal. Most digital noise-reduction systems are of the Single-ended type.

The waveform of a pure sinusoidal tone which has a waveform defined by a mathematical function derived from a classic periodic oscillation, such as the movement of the tip of swinging pendulum. In a musical context, a sine wave contains only a single fundamental frequency, and  no harmonics.