Prophet 600 Noise Mod and Gligli update

V2.29 includes: CC 56 and CC74 previously did not let you select the full compliment of LFO/Vibrato waveforms over MIDI. That has been resolved. Added new CC 77 (Poly Mod Filter Env to modulate VCO A, VCO B, or VCO AB). UI sped up to V2.26B speed. Existing bugs I need to work on:  CC  76 (Vibrato Target) is not working correctly. I'm not sure why. Release: Version 2.29 JS .hex and .syx files zipped here: Download Source code: https://github.com/matrix12x/p600fw

I updated the OS to version 2.28. This adds "To Tape" + 444 menu option for assigning the poly mod filter env to modulate the pitch of VCO A only, VCO B only, or both. This is great for the creation of brass sounds and EDM leads. The default is the factory VCO A only. Here is the link to a .ZIP for the .SYX and .HEX file p600firmware V2_28.zip

So, I don't like how the Prophet 600's VCO A changes in pitch (not just timbre) when using Poly Mod VCO B to modulate the pitch of VCO A even on the original factory OS. It is not a software thing, it's the hardware itself.  The circuit that feeds VCO B's output to the CV input of VCO A is not AC coupled (it does not have a DC blocking cap). Thus a DC offset is introduced which changes the tuning of VCO A by raising the pitch. I hate this. I never use Poly Mod VCO B to modulate the pitch of VCO A.  I held down a single note with Saw wave selected on VCO A and VCO B was zero volume. No  Poly Mod . Here I added some FM (frequency modulation) to VCO A (Saw wave) in an unmodified Prophet 600 by using Poly Mod VCO B to VCO A frequency. If you look at the fundamental, it goes up in frequency relative to the first image. My thought were to mod the Prophet 600 to add a DC blocking cap, for example between the 4061 (e.g., U429 pin 1) and the CV in (pin 15) for ...