[sdiy] Thoughts on a Polyphonic Synth

[Tom Arnold]

On Fri, Mar 24, 2006 at 10:35:15AM -0500, harrybissell wrote:
> And a way to keep them all in tune. Usually they use a computer
> to measure the frequency error and compensate per MIDI note number.
> Lookup table kind of thing...

So, this actually brings up a subject I am much interested in...

How could you autotune/autoscale a standard sawtooth core VCO?  I suppose
there are the not so nice ways like using electronicly controlled resistors.
Tuning I suppose isnt that hard, you just use a DAC to inject an offset
voltage.  A lookup table per note isnt, IMHO, the best way to do this
because that wont work well for odd things like microtonal.  Well, unless
your lookup table is rather large...

And then theres the whole part of the actual frequency measurement.  What
would we do there, just time the reset pulse of the core?

I'm guessing this isnt "easy" to do or everyone's pet vcos would be
autotune. :-)  However I need a test environment for a poly-ish toy I've
been playing with for a while and having 32 oscillators in tune would be
extremely nice...
 
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