Seeds VCO from Ginko Synthese build and demo video up.

A VCO with a built-in Attack/Release envelope that you can use, or use your standard enveloping.
Quick build. Does not have the presets I expected, just one, but it’s programmable.
OK sound (not quite to my taste) and reasonably small.

Build

Follow up to the above, I was not selecting patches correctly, here's how you do it

Patch select