Right now it only supports #PLAY statement chiptunes (albeit with multiple channels and a few effects):http://www.chriskallen.com/zzt/hallofmu ... allofmusic
But you definitely aren't alone in wanting MOD, MIDI, MP3, and possibly OGG support. Such formats are on my "advanced features" list.
MIDI, unfortunately, would be one of the more difficult formats to support because uncertain soundfonts make a mess of how any one tune "should" sound when played back. WAV and MP3 would be easy, and MOD would be slightly harder, but MIDI is the only one I'd consider hard to the point of controversy.