Lately I've been building a lot of new modules, the most recent one being an envelope follower. Basically it converts amplitude to voltage. One way to use it is to take external input (like a drum machine, the radio, etc) and use its amplitude envelope of to control something else. For instance, if you take the audio output of an iPad running Korg Gadget playing a drum groove and take the CV output of the envelope follower and plug it into the cutoff of a filter, the filter cutoff will modulate based on the loudness of the drums. In other words, you can extract the amplitude envelope of one thing and use it to control another thing. As I understand it, this is how auto-wah filters and some kinds of compressors work! A cool little circuit.

Here's the envelope follower built and installed into the modular, using the radio as an envelope source, controlling all sorts of things:

https://www.instagram.com/p/BCQR2pHpHfC/

Here's a quick improvisation from last night when I had the envelope follower on the breadboard.

Korg Gadget running on iPad goes into a preamp, then into the envelope follower, and also one input in a mixer.

The output of the envelope follower controls the cutoff of a low pass filter, as well as the clock of a sequencer.

The sequencer sends CV to a pair of saw wave oscillators, which then go through the low pass filter, then finally into the mixer with the drums.

Check out the audio here:

http://www.chrisbeckstrom.com/korg-gadget-dual-saw-vco/