Here’s what he has to say about the performance:
The game music was originally composed by Douglas Fulton for the Apple IIGS, but a number of ports were made and C64-hero Rob Hubbard arranged some of them for NES (which my version is based on).
The PO-32 takes care of the bass line and some percussion (all sounds were created in Microtonic and then transferred to the PO). The PO-28 handles live playing and background melody. PO-32 feeds 28 with sync and its audio and everything is then recorded straight from the PO-28 output. No mixing or post processing added.