General MIDI is an industry-wide set of specifications for sound sources that allow music data to be created regardless of manufacturer or specific models. General MIDI defines the minimum number of voices that should be supported, the MIDI messages that should be recognized, which sounds correspond to which Program Change numbers, and the layout of rhythm sounds on the keyboard. The General MIDI logo on a sound source indicates compatibility with song data which also carries the General MIDI logo.

GM2 (General MIDI System Level 2) is a set of standards for editing voices not covered by GM1. GM2 also defines the operation specifications of effects and other elements in detail, and enables more sophisticated performance expression and greater compatibility, by expanding range of voices.