MOTM

A HA! Somebody noticed!!

OK...what you are hearing is the over-driven VCF has a sine-wave oscillation
going on
"in the background" with high Q. This is not tracking the VCOs exactly, so
you hear
a beating between the VCOs and the VCF. Pretty neat, huh!!

This is in file m420-1.mp3 I really didn't "tune" the VCF 1V/oct to a VCO
because I think
the "randomness" of the harmonic beat frequency sounds better. This is a
trim-pot on the pcb.
2-3 octave is about the best you can hope for (using the VCF as a VCO!!).

Paul S.