MOTM

Correction on the patch explanation, sorry:

Oscillator --> Filter (Audio In) --> Envelope Follower (Audio In)
Envelope Follower (Mod Out) --> Filter (Mod In)

Envelope Follower Audio Out --> Computer / Audio Mixer

The feedback is caused by the filter going into the envelope follower
while at the same time the envelope follower controls the filter
cutoff.

Less freq cutoff = more volume = more voltage from env follow to freq
mod = less freq cutoff