A set of requirements for MIDI devices aimed at ensuring consistent playback performance on all instruments bearing the GM logo. Some of the requirements include 24-voice polyphony, a standardized group (and location) of sounds, as well as defining a limited number of controllers. For example, patch #17 will always be a drawbar organ sound on all General MIDI instruments. Continuous controller number 7 will control its volume. Music written and sequenced for General MIDI should play back with the same instrument sounds on any General MIDI (GM) sound source.