I've heard polyphonic music output from a 6809 running at 0.9MHz. AFAIK it
was squarewave sources mixed in software then output through a simple
weighted resistor (not r2r) DAC. I think I would be tempted to do some of
the waveshaping in hardware, say with two pic pins per 'voice', one charging
a largeish capacitor for envelope, and the other 'chopping' it using a diode
or transistor. This could give a simple 'ding' sound which may be
acceptable, with the PIC only outputing squarewaves.

Obviously the passives count would be high.

Table synthesis would be great, you could do anything, but I would expect it
to really eat cycles. Can't say I've tried though.

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