I can't believe it's not a VCO

PCB set = USD20
panel = USD20
assembled = USD180

This module is based on ideas presented in Electronotes #132. It is a VCF with a 'filter exciter' section to allow a wide variety of acoustic, semi-acoustic and not-acoustic-at-all sounds. In a sense it takes the concept of pinging the LPG or ringing a VCF one step (or 2) further. The decaying sound is fed back into the input via a VCA. The VCA can be controlled by a gate or an envelope (or both).
Another interesting point is higher frequency sounds tend to be louder.....which is what happens naturally in the big room.

Build guide & panel template on the NLC wiki