“MMA—Musical MIDI Accompaniment” is an accompaniment generator. It creates MIDI tracks for a soloist to perform over from a user supplied file containing chords and MMA directives.
MMA is very versatile and generates excellent tracks. It comes with an extensive user-extendable library with a variety of patterns for various popular rhythms, detailed user manuals, and several demo songs.
MMA is a command line driven program. It creates MIDI files which are then played by a sequencer or MIDI file play program. More Info »
Gek S. Low has also written a nice little GUI front-end. He refers to it as a “lazy man's” program to make it easier for folks to enter simple chord progressions. It's written in python and tkinter. Get Lemma at http://xenon.stanford.edu/~geksiong/lemma.html .
See http://www.mellowood.ca/mma/helpers.html#editors for syntax coloring in editors like Emacs, Kate and SciTE.
There are scripts to convert data files from other formats like Band-in-a-box, ABC, MUP and Yamaya .sty (see http://www.mellowood.ca/mma/helpers.html#convert )