General MIDI


(n.) General Musical Instrument Digital Interface; a standard configuration for MIDI systems. It refers to the assignment of particular sounds to specified preset locations. General MIDI sequencer files should sound roughly equivalent when executed by a variety of sound cards or synthesizers. This is not always the case, given the extreme differences between the sound of FM synthesizers and wavetable sample players.

Specifically, MIDI is a mapping structure that assigns instrument sounds, or voices, to each of the 128 different presets, programs, or patch locations. In a multitimbral MIDI sequence, each musical part or voice is sent to a different preset according to a “patch map.” General MIDI defines the type of sound that resides at each patch location. There are 16 groups of eight instrument types. MIDI programs may be assigned to MIDI channels, and a sequence of note-on and note-off events may be sent to each discrete channel. The determination of which voice responds to which channel is controlled by a system message that sets up the receiver.

General MIDI specification sets the first 9 channels for instruments and the 10th for percussion. The remaining channels, 11 through 16, are left open for user configuration. Because early generations of sound cards were unable to support all 16 channels, Microsoft devised a proprietary system for assigning MIDI voices in Windows. In this scheme, Basic MIDI devices use MIDI channels 13 through 16. In a more evolved system called Extended MIDI, devices use channels 1 through 9 for instruments and channel 10 for percussion; no assignments are possible for channels 11 through 16.

The first of two linked tables shows the General MIDI instrument program map. In addition to the 128 instruments listed in this table, the General MIDI specification assigns 47 drum sounds to a “key map.” The second table shows the General MIDI percussion key map. The percussion instrument assigned to each note number is named. For your reference, middle C is note number 60. Click to open General MIDI Maps.

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