Commodore 64

Synthaholic AKA sPEW chordman at
Sat Mar 1 22:02:47 CET 1997

On Sat, 1 Mar 1997 11:54:21 -0700, you wrote:

>>I'm considering building a synth and integrating one of my half-dozen or 
>>so spare C64's as a very programmable controller, waveform generator and 
>>ADSR generator.  Has anyone else done this?  Is this a wise thing to do? 
>>I know it'll save money...  :)

I haven't any experience with C64 machines, but I built a 4 voice
synth (polyphonic) using a SWTPC 6800 which ran a sequencer and drove
a digital mux system that selected tones from a top octave generator.
Each channel also had an AND gate array to select a combination of 4
octaves generated by binary counters.  These 4 voices then ran to an
analog mux to send the signal to one of 4 simple RC filters.  Not very
robust filter-wise, but it was 4 voice polyphonic, and dang it, it
actually sounded pretty good.  Since the synth had it's own latches,
the computer could be dedicated to sequencing, so even at it's slow
clock rate of 1 mhz, it could actually do this accurately.  The code
was written in assembly.  Timing was kept accurate using a crystal
controlled interrupt timer/clock.

I dug out that old 6800 a while ago and it still works!  I keep
thinking of making a wave table synth (single voice) with two
externally clocked memory planes so that while one is producing sound,
the other can be loaded with a different wave.  When the new wave is
loaded, the computer could switch planes.  The result would be a
morphing waveform.

Dang, if there were just 8 more hours in a day or would that I didn't
need to sleep...
- Scott Gravenhorst (Synthaholic)

Programming: The Ultimate Computer Game. | Windows 95: The Ultimate
Unfortunately, you never win.            |      Pain in the Butt

"I didn't do it."
   -- Bart Simpson

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