Post by solipsistnation on Sept 6, 2022 0:58:14 GMT
I have come up with a way to do not-very-good polyphony. Let me describe it. Here is the basic poly rack:
And here it is all patched up:
Here's the basic idea:
On each keypress, I want it to send trigger and CV to a different voice (where a voice is a basic oscillator/envelope/vca). Those get sent to a mixer, which goes to the audio out.
There are 2 things to multiplex-- CV and trigger.
The gate input from MIDI goes to the _clock_ input on the SEQ8, so each MIDI keypress steps it forward once. The SEQ8 is set up with 4 steps, with step 5's trigger out patched to reset. Hit a key on a midi controller 4 times and it will step through the 4 steps of the sequencer.
SEQ8 CV out is sent to the SWITCHMATRIX CV input. Each SEQ8 step selects a switchmatrix patch that sends input 1 to outputs 1, 2, 3, or 4.
SEQ8's step trigger outs are patched to envelope 1 through 4.
Each voice is a 2OSC/d oscillator going to the QVCA input, and each of the 4 VCAs is controlled by one of the 4 envelopes.
So now, as you hit keys on your MIDI controller, it triggers each voice in turn, and then loops back to voice 1.
This appears to work!
What I ran into, though, is that it seems like the 2OSC/d's oscillators don't like it much when the CV goes away, and since it gets switched out each step (and sent to the next oscillator in turn), they stop making noise or just do something weird-sounding. Even though the envelope decays are still hanging on, each voice goes silent as the next one starts, so it ends up acting like a single voice with a lot of extra steps.
Otherwise, I think this has promise. It might need 4 S&Hs to keep each voice going, and I don't think I have that, and there's not space in my little rack here.
Thoughts? Ideas for making something like this work? Adding filters would double the envelopes, but would just mean multing each step trigger out and triggering the filter envelope at the same time as the amp envelope. (Or you could go Korg Poly-800 style and have a single filter for all 4 voices, with an envelope that retriggers on each keypress. That would be easy, using just the SEQ8's trigger output.)
There's also no reason to keep each voice set up the same-- you could pretty easily turn this basic rig into a poor man's (or at least a reasonably middle-class man's) Korg Mono/Poly. And I'm underusing the Switchmatrix. How about 2 oscillators per voice? 8)
8 voices would be difficult since you'd have to multiplex through 2 switchmatrices. It wouldn't be impossible, though (probably just using step 5-8's trigger outs as both envelope triggers AND to flip a VCswitch or something like that). How about a giant 4x20 rack set up as a ridiculous 8-voice monster polysynth?