For guitars and other instrument-level signals I recommend starting with the "2164" filter plug-in boards, because these have very low noise and CV feedthrough.
Other plug-in boards will work for guitars, but may be a little noisier and thumpier than you wish. Try them out, they vary.
If you're using this in an effects loop or after a preamp, it doesn't matter as much and any of them will probably be fine.
Manual frequency and resonance controls.
Digitally generated LFO with morphing waveshaper, smoothly crossfades from triangle to sine to square to sample & hold.
Analog envelope follower for when you want to quack and bwow instead of whoosh.
