I don't
know what you consider to be 'original Mac', but the Mac+ sound
hardware was a pulse-width modulator loaded from a spare byte in the
video RAM area at the end of each video line.
I think we're looking at this from different angles. I'm looking at it from
the view of what the Toolbox offers for music playback and synthesis; it
seems you and Jim are actually talking about what the Toolbox is driving.
You must know me by now... I probably don't even have the relevant volume
of Inside Macintosh, but I am not against taking a soldering iron and
multimeter to a bit of hardware ;-)
-tony