Hi Lugia,
if you look more closely - there are 8 VCA's in the rack-the two modules at the far right on the bottom row:
https://www.modulargrid.net/e/erica-synths-black-quad-vca
"Controlled chance" as you have stated or constrained randomness in the harmonic and melodic progression is exactly the goal of this build.
Maybe I'm thinking about this wrong, but I've been looking at the system design as 4channels which are interrelated harmonically:
Melodic arpeggios
Harmonic progression ( chords )
monophonic base
Percussion
With each of these "channel" requiring it's own sequencing, but remaining related via the quantizer and fundamental clock rhythm. Ideally each of these channel progressions are allowed to evolve independently ( at different rates )
more research, I guess...
thanks for the comments,
cheers,
-m