Resonate

4 stage VC bandpass filter

This uses the core circuit of the Korg 3100 Resonator, with component choices for the filter sections as per the mods introduced by RJB in his blog back in 2005.
The main difference of this version is that it has 4 VC bandpass stages and a feedback control, the original has 3 stages and no feedback. The 4 VC bandpass stages can be controlled by a single CV on input 1 (with an attenuator) or individually with each of the 4 CV inputs.
The CV processing sub-circuits are greatly simplified from the original Korg version, simply using op amps to drive the vactrols.
The 2 inputs are summed together. Out 2 is an inverted version of Out 1.

https://www.nonlinearcircuits.com/modules/p/resonate