MIDI Protocol
A 1983 performance-control protocol that carries instructions, not sound
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MIDI is a control protocol agreed in 1983 by several electronic-instrument makers. It carries performance instructions such as note on and off, velocity, controllers, program changes and clock, but no audio waveform. The sound you hear is produced by the receiving synthesizer or sampler.
One MIDI connection can carry 16 channels, and most message values are 7-bit, from 0 to 127. Devices use the channel number to decide which messages to answer. A sequencer records these messages and sends them back to a sound source on playback; pitch, velocity and controllers each have their own encoding.
The usual mistake is to treat a MIDI file as an audio file and assume it has a sound quality of its own. The same MIDI file can sound completely different through another sound source. It describes how to play, not the final sound.
Related → Velocity
Sources
- MIDI 的消息结构、通道与 7 位数值范围，参 MIDI 1.0 Specification（MMA, 1996）与 The New Grove Dictionary of Music and Musicians, "MIDI"；本文为原创表述
Used for fact-checking only; all prose is original.