MIDI
Industry standard for exchanging musical control information between electronic instruments.
What it means
MIDI stands for Musical Instrument Digital Interface and is an industry standard for exchanging musical control information between electronic instruments, computers and other devices. Importantly, MIDI does not transmit sound but instructions, for example which key was pressed, how hard, and when it was released. The receiving device produces the tone from them.
The data are transmitted on up to 16 channels. Messages include note on and note off with velocity, program change for choosing a sound, pitch bend, and controllers such as volume or modulation.
Musical use
MIDI 1.0 was introduced in 1983 and made it possible to connect synthesisers from different manufacturers. It remains the basis of computer music production today. In Standard MIDI Files, pieces of music can be stored as sequences of notes; these are very small but sound different depending on the sound generator. A revised version, MIDI 2.0, was published in 2020.
MIDI should be distinguished from audio files such as WAV or MP3, which store the sound itself.
Performance practice
When working with MIDI, separate input from sound: you can play the same recording back with different sounds. Watch your timing when recording and correct velocities, rather than only changing the instrument's volume.