It started with reading about the Olegtron R2R: www.olegtron.com/olegtron-r2r-1 That module is literally just a chain of resistors with patch points connected to the chain with more resistors I have resistors, so I built a clone on a breadboard
Further down the page, there's an explanation on how to use such a chain of resistors as an 8-bit DAC. Byte beat is unsigned 8-bit audio at 8KHz There are enough pins on one side of the Arduino Nano to just dump the 8 bits of such a formula, plus a clock output, and maybe even a couple parameters, to pick from formulae and tweak a number in there.
It just occurred to me over lunch that the separate bit outputs (the 8 coloured cables coming out of the Arduino) can also be used separately, not just summed through the R2R What this means is eight noisy square waves that not only have some rhythmic structure to their noise, but are also congruent to each other. I tried using one to trigger an envelope that drives a filter while another modulates PWM on the VCO, and it's crazy!
Will record some of this insanity soon and post it!