MOTM

I don't have any fast rule, and as others have said, the modules will keep
moving around as the machine grows...

But in general, if I have three rows high, the top row is where I stick
sources, the middle are modifiers, and the bottom controllers. Since a lot
of modules have multiple functions, that still leaves lots of room for
playing around. Also, I do tend to lay them out for typical flow from left
to right within the above structure, so VCA's & EGs "tend" to be toward the
right and VCOs, LFOs, etc. to the left. But again, no concrete rules. It's a
modular after all; it's entire raison d'etre is to be flexible.

I don't concern myself with multiple voices. When I think of my modular,
polyphony never occurs to me. To paraphrase Carlos, the more modules I have
available, the more I can refine one single note. So with ten VCOs, I would
still be tweaking nuances of a single voice, not trying to make a 10-voice
Korg MS-10.