Hiya folks, to keep it short:
The game runs mostly fine, but if there's any kind of fade between scenes, the sound breaks up irritatingly.
If I lower the refresh rate to something stupid like 5hz, the problem goes away because the emulator only has to draw every so often and the fade is basically unnoticed.

I've tried various combinations of CPU speeds 'n' memory amounts and I mucked about with the JIT compiler options, but I just can't get the thing performing perfectly.
Only thing I haven't tried as yet is to run a different ROM file (at the moment I have one called 'quadra650.rom').

Glitchy sound during fades and transitions is also a problem in Sheepshaver, so - throwing the floor open to anyone who has advice on how to get this stuff running as intended.