I have an old version that I installed on my 97 486 and from what I gathered, it was basically an easy way to "create" or to input background music for pop-type tunes. To do this, you'd need the chords of the piece. For example, the common chord progression I-IV-V-I is easy to input. You could select from a variety of accompaniment patterns that reflect common styles of different bands such as Paul Schaffer or Doc Sevrenson. The program would then automatically create the background percussion, bass, chords and such so that you can play or sing along with the melody. I think that you could also include the melody by inputting the individual notes and/or vocal lyrics. The playback sounds were sound-card MIDI.
Here's some examples:
http://www.pgmusic.com/ubbthreads/showflat.php?at=0&Number=156967&an=0&page=0#Post156967
I don't think that this is too useful for classical music performance where the acc. rhythms and chords are more diverse and random.
To do something that is fairly decent with MIDI you'd need to have either a score program such as Finale or a MIDI sequencer such as Cakewalk. With these you'd input every note individually or multi-notes as chords. You can add some finer things such as ritards, crescendos, slight less defined note-location and vibrato with MIDI to make the performance less pristeen or plastic and it can then sound fairly lifelike if one really gets into the finer aspects of editing.
The program of preference these days is Smart music. There are a lot of acc. files that one can get but it doesn't allow the player to interact with a real person(s) in the accompaniment.
