I asked Mike a similar question via youtube, and he told me that any of the sequencer tracks can trigger any of the internal sounds. For example, though tracks 1-5 are labelled for drums in the manual, they don't have to be used for drums. Based upon this, I'd say you should have 8 monophonic tracks for whatever internal sounds you want to trigger with them, 1 polyphonic track, and 4 controller tracks. How this applies to external instruments via MIDI, I can't answer. I trust happyrat knows of what he speaks, however.