I started this a wile ago, got frustrated and dropped it. Today I decided to give it another go.
I don't love the idea of the daughter board where LFO ticking may get wild, but just couldn't arrange it on the main board without it getting awkward.
Anyway, no identification on LED and LDRs used, so even if this drawing is correct, you might have to experiment a bit to find out a good combination.
Any extra pair of fault-finding eyes would be nice :)