[sdiy] DIY polyphony handler

D. Hamara ishkabbible at gmail.com
Wed Jan 23 06:34:04 CET 2019

Polyphony is harder than it sounds. There are a lot of gotchas in the 
details, as I discovered when I designed my own polyphonic MIDI 
interface. How does the interface know when a voice is done with all of 
its envelopes? When is an exponential envelope "done"? If all the voices 
are busy, which one gets "stolen" when a new key is pressed? When are 
trigger / gate signals issued (staccato vs legato).

And things one simply expects from a monophonic synth, like portamento, 
go from simple to incredibly complex (which voice glides to the new note 
you just pressed? If there is an unused voice, what note do you start 
the glide from?).

And if you actually want to play chords, you need some way to make sure 
that all of your voices sound the same given the same CV inputs.

That said, it is possible. I did mine on the Teensy 3.2 with an external 
16-bit DAC (there are a BUNCH on the market to choose from), driving my 
eurorack configured as 4 x 3 oscillator voices. And it does work:


On 1/22/2019 12:05 PM, ulfur hansson wrote:
> hello list!
> i have a few diy voice “cards” (meaning various prototypes ziptied together) of my own design laying around, and have been thinking it’d be neat to build a 6-voice midi CV/gate handler for polyphonic playing.
> all parameters are currently voltage controlled, so building a rudimentary knob control panel is easy - however, when it comes to choosing DAC’s and microcontroller platforms, i’m a little lost!
> does anyone have experience building a basic setup like this? i’m thinking up to 8x round robin pitch CV’s and Gates.
> (bonus feature; DIY autotune anyone?)
> thanks!
> Sent from outer space
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* Dave Hamara                         ishkabbible at gmail.com        *
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