Thanks for the extra details, so far I have reversed in MAME the Z80 sound logic from oriental legend and wrote a simple sound driver which works on MAME but it fails on real hardware, something small I'm missing there no doubt. I'll take a look at this and see if we can nudge it along.
Would love to help out experimenting more with this, I've never seen a reference to a "Disposable demo" though? I saw there was a simple Chaos demo for IGS PGM though. I'll try to see if that works.