Midi computer files are a complex series of musical notes translated into computer language. The actual sounds are not recorded in Midi files; these must be produced by the musical instrument or sound card that interprets them. A Midi file only contains such information as the pitch and duration of notes, the channel and patch to which these pitches and durations are assigned, and the velocity, or loudness, of each note.
Midi is an ideal medium for displaying music files on the internet, for two reasons: First, they can be recognized by any web browser (as long as it has the appropriate plug-ins), and second, the files take up much less space than audio files, since they contain only the basic data needed by the instrument/sound card to recreate the music.