A subset of the MIDI specification which is a minimum 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 128 sounds, that the synthesizer be 16-part multitimbral, and provides for a standard pitch encoding. Some manufacturers have proposed supersets to GM, e.g., Roland’s GS and Yamaha’s XG.