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.

These kits and assembled modules are offered on demand, click the link to learn more.