All About MIDI
The different types of MIDI Music
1. General MIDI
General MIDI is used to standardise an instrument programme number map. There are 128 GM Instruments altogether. The patches are arranged into 16 "families" of instruments, with each family containing 8 instruments. The 16 families are: piano, chromatic percussion, organ, guitar, bass, solo strings, ensemble, brass, reed, pipe, synth lead, synth pad, synth effects, ethnic, percussive, and sound effects.
However, it has its limitations: firstly, there is a limited size of the instrument palette (128 instruments). Some instruments are constant in their programs -- Acoustic grand piano is always program 1. Glockenspiel is always program 10. French horn is always program 60. Recorder is always program 75. MIDI Channel 10 is usually for drum kits. Secondly, it is unable to add customised instruments to suit the needs of the particular piece. Thirdly, it has the lowest-common-denominator character. Afterwards, General MIDI is splited into General MIDI 1 (introduced in 1991) and General MIDI 2 (introduced in 1999).
2. General MIDI 2
General MIDI 2 is developed by companies in Japan's Association of Musical Electronics Industry . The main improvements are the increase in instrument palette, specifying more message responses detailedly, and defining new messages for custom tuning scales etc. It is maintained and published by the MMA and AMEI.