MIDI is an acronym for Musical Instrument Digital Interface. It is basically a sequence programming protocol, commonly used for composing
music. The concept for MIDI was invented in the
80's when there was no common communication standard between synthesizers. Over the years, it has gotten a reputation for sounding like crap. What people keep forgetting, is that MIDI isn't responsible for producing
sound. The synthesizer is. Most
music teaching programs, like Synthesia, use MIDI files.
The most common MIDI files utilize General MIDI 1.0, although there exists MIDI 2.0, with
HD-MIDI being in development right
now. Unfortunately, GM 2.0 isn't supported by a lot of synthesizers.