Midi files may not seem like a very exciting format, but it's a format that I can import into Finale to create notation for traditional instruments. Not to mention, data-bending or arbitrarily manipulating a Midi piece could yield interesting results.
There's also the [midifile] object now in: http://pure-data.cvs.sourceforge.net/pure-data/externals/mrpeach/midifile/ It can record as well as play.
Martin