Thanks to blargg's macro pack, I managed to bring up about 20% of my Pently music engine on the SPC700. It's still missing host communication and several effect commands, but the basic structure of a timer feeding a tempo divider feeding conductor track and pattern interpreters feeding a note-on engine is there. So are synthesizers for crude hat and guitar samples, as well as the kick and snare samples I made a decade and a half ago when I was using ModPlug.