This is a cool sounding filter. I've replaced the cutoff pot with a couple of 2-22k LDRs and used this
Super-Simple Dual-Wave LFO. Sounds very cool! A nice leslie-esq filter, sounds similar to the filter side of the
Tremshifter.
I replaced the 68k resistor in the LFO with a 100k trim and dialed that in by ear. I'm getting a fair amount of ticking on the square side, but close to none one the triangle side. So I'm sure that's caused by the LED turning on and off. If anyone's got a suggestion to clean up that ticking, that would be awesome. This could make a great addition.
The 10k pot seems like it may be too much (maybe I'm backwards - it was late last night), I was getting a lot of whistling for most of the rotation. I'll try a 1k or 2k pot tomorrow.
Thanks for the layout!