A MIDI file is a sound file in standardised format containing MIDI (Musical Instrument Digital Interface) instructions sent to a synthesizer which converts them into notes of music. Note(s): A MIDI file contains no digital sound but merely receives commands for driving MIDI instruments. A MIDI file contains data on each of the notes to be played (including duration, volume, key, track number, tempo etc.). Thus, instead of writing notes on scores, you can compose music by programming MIDI files. A MIDI file is actually a digital representation of a musical score. There are two types of sound file: sound wave files (actual digitised sounds) and MIDI files (instructions for producing music). MIDI files generally have the extension .mid.