Midi (short for Musical Instrument Digital Interface) files are very small files that contain musical score. They can be played on computers, where software is used that contains sounds that correspond to the instruments that are programmed in the midi files. So lets say you write a midi score for an organ, when you play that back, the software will play the score back using sounds that emulate an organ, to the best of its abilities. It really really reduces music to its formal essence, because there is no soul playing it back. It's just the computer running the script. This format then, seems to be used a lot for Gospel tunes. I first noticed this when I heard it playing in the background of the Chibi Jesus website. I have included only a couple of examples here.