Instead of the basically useless fuzz adjust control and mildly useful two position switch, wire it up like so for a sweepable low pass kinda thing. I also threw an MPSA18 in Q5 for a bit of oomph on the output.
I really love this circuit! It cleans up ridiculously (like roll back to 7 and it’s a little gritty), the octave is very pronounced (I used 1n5817s all around again) and it nails that nasty FZ-2 sound with way less parts haha.