[sdiy] polyphony & ken stone's 16-key keyboard controller?

[anthony]

I have been planning to make 2 of Ken Stone's 16-key keyboard controllers 
for 2 small monosynths I am working on. I'll be using 74C923's instead of 
74C922's though because I already had those. With the 923 I can make a 
20-key keyboard. Sine both synths will have 2 VCO's I thought it might be 
neat to figure out a way to get something like 2-note polyphony since from 
looking at the schematic and how the control voltages are derived it seemed 
feasible. I have some CD4044 CMOS 3-state latches and they seem like just 
the thing.

Since the 92X's latch their own output, the gate signal would trigger the 
ENABLE pin of the 4044 latching the current output and holding it when a 2nd 
key is pressed and then latching the output of the 2nd one when a third key 
is pressed - resulting of course in the data latched from the 1st key being 
lost. This concept relies heavilly on the way the 92X works - especially the 
way it deals with more than one key being pressed. The tricky part may be 
getting the 2nd gate to work properly.

The original ciruit as designed by Ken is superb & elegant - doing what it 
does with so few parts.

aa