A Paraphonic synth can play different notes, but they share a signal path, so same VCA, VCF etc. A Polyphonic has everything for just one voice.
My design is a controller board, that sets parallel CVs and oscillator selection etc, that's shared to all voice boards, then there is a seperate ADSR for each voice, so when a new note is pressed it is all re triggered.
The ADSR are PIC micros programmed from Electric Druid.
A comment on instagram suggested I build the entire voice circuit on one PCB (including the ADSRs and DACS) If I was building this again I would consider that, but I will explain my choices for why i've done it the way I have.
First this took a bit of experimentation and the whole thing was built in stages, the ADSRs need all the CVs together in parallel, so putting this on a seperate board made this easier, then all I need is the CV out back to the voice, the ADSR board has the DACs too.
Having all the voice DACs on the main board was easier with the SPI bus and testing during programming, also it keeps all the adjustment pots for the 1volt/octave all together.
The parallel CV DACs have to be on the main board as these are shared to all voice chips
If I was to do this again, i'd put the ADSR chip and voice DAC on the main board, but keep all the general CV DACs on the main board
Instead of one big PCB each voice is seperate for 2 reasons: to use all the boards I get from the manufacturers wher teh minimum is 5, and to make troubleshooting easier