Ok, I’ve started soldering my own build (thanks again for the board @crucFX!) and digging back into all my notes here and references noted above since my original suggestion for writing up the cross nodes seems not to be correct. I reread this bit from Richard Brewster’s page on making his Tetrazzi modular:
Quote:Shown above is Peter B’s schematic for one of the four Tetrazzi oscillators. It is an ingenious design for a voltage-controlled sawtooth/ramp oscillator, where the up and down rates are separately voltage controlled. Not only are the rates under VC, each VCO has two modulation inputs, one for up (UPMOD) and one for down (DONMOD), that are hard-wired internally to come from the other VCOS. The internal patch looks like this:
UPMOD cross connections: [1 -> 4; 4 -> 3; 3 -> 2; 2 -> 1]
DONMOD cross connections: [4 -> 1; 4 -> 2; 2 -> 3; 2 -> 4] Unquote.
This lead me to consider that there are two nets of cross modulation not just one. (I am making the assumption that the numbers here refer to quadrants and not the cross number.) In the schematic above, the DONMOD pot is on the left and it’s modulation point is 1 Star. The UPMOD pot is on the right and it’s modulation point is 2 Star. Within each quadrant the are 2 similar crosses and these have to be connected together to match the schematic. This is the “3 star” and “channel out” area I marked just above the piezo in the schematic. As noted before, I based the schematic off of the bottom left quadrant. Let’s call this quadrant #4. Above it is #1 and clockwise to #2 and then #3. If you connect those two 3 stars together and then to the 3 star in #3 it begins to follow the UPMOD pattern. Here’s all four color coded:
The UPMOD bit makes sense to me and kind of what I thought the whole scene was, but the DONMOD isn’t circular as Richard describes it. What you do get if you connect the remaining similar crosses is another circular pattern like so:
I’m still not sure if this is right but it’s closer to what Richard described.
One more detail is that until now I didn’t realize that quadrants #1 use different input pins to the 4051 than quadrants #2. I think this another way to add chaos to the interweaving of the oscillators.
EDIT: I just read this again and I realize it’s not as clear as it could be (like all my posts in this thread. 
) I’ll look at all this again tomorrow and see if I can make it more plain.
