Synth module

A sound module is an electronic musical instrument without a human-playable interface such as a piano-style musical keyboard. Sound modules have to be operated using an externally connected device, which is often a MIDI controller, of which the most common type is the musical keyboard (although wind controllers, guitar controllers and electronic drum pads are also used). Controllers are devices that provide the human-playable interface and which may or may not produce sounds of its own. Another common way of controlling a sound module is through a sequencer, which is computer hardware or software designed to record and play back control information for sound-generating hardware (e.g., a DJ may program a bassline and use the sound module to produce the sound). Connections between sound modules, controllers, and sequencers are generally made with MIDI (Musical Instrument Digital Interface), which is a standardized protocol designed for this purpose, which includes special ports (jacks) and cables.

Sound modules may use any number of technologies to produce their sounds. A sound module may be an analog or digital synthesizer, a sampler, or a rompler. Electronic drum module are sound modules which specialize in percussion sounds. Drum modules may be triggered by external trigger pads or pickups as well as through MIDI. Drum modules are distinguished from drum machines through their lack of dedicated on-board triggers and lack of an integrated sequencer. Sound modules are often rack-mountable, but might also have a table-top form factor, particularly when the intended user is a DJ or record producer. The height of a sound module is often described in rack units ("U") or unit. Small sound modules are mostly 1U in height, the larger models a multiplication e.g. 2U or 3U. Despite the name, "sound module", most sound modules do not produce any audible sound until their output is plugged into a keyboard amplifier and loudspeaker or a PA system.

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