MIDI is the standard used to connect digital audio devices to a host computer or other devices, typically on high-end digital audio workstations.
Often, these devices require separate interface cards to connect to the host computers that perform all MIDI communications.
But the standard was also made famous by the .mid file format, due to the open specification that gained industry support. It is flexible because the format described data types that are used in its communication for device ID, pitch, velocity, step, and loop-starting states.
Perhaps the most famous MIDI file was canyon.mid:
The thing that I find facinating about the original canyon.mid is the use of Syncopation, bordering on Tempo rubato (stolen time) near the very end.
And here's a cover of Canyon by Jake Kaufman. This one is exceptional because it lines up perfectly with the original version, above (including the Syncopation aspect):
