How to randomly transpose two patterns the same way?

[mvdirty]

I have not yet fully understood the reason and it may very well be the timing mentioned in that other thread (just read it once and I guess I have to revisit it).

To summarize the most relevant bits: You’d be tempted to output a transposition value from one track on the same tick as you’d expect another track to be transposed by it, but between things like physics, software engineering, etc. the transposition voltage won’t be seen and processed until just afterward. As such, you may need to transpose a little earlier. This can be a little annoying/challenging if wanting to transpose at the start of a pattern, for example.

Anyway, I'm making progress.

Excellent!