It's halfway between a Sallen Key and State Variable filter in tone, here is a quick rundown:
Sallen Key: Warm tone, growling resonance which gets drowned out with large drive
State Variable: Cleaner tone, cleaner resonance which stays strong with large drive
1/2 way between the two: Warm tone with growling resonance that stays strong with large drive
It is a non-linear variation on a Sallen Key, but I've not seen this exact structure before in any schematics, I came up with the idea independently, but I am not ruling out it may already exist since there have been a lot of people making a lot of resonant filter circuits for a long time. I am thinking of calling it SMP, (S)tate Variable (M)S20 (P)artnership, which by coincidence happens to also be some of the letters from my surname
PS: It is already implemented and will be released in the new version of The Drop in both high pass and low pass, 2 and 4 pole, and it will provide yet another sonic variation to choose from to either subtly sculpt or drastically distort your audio.
So now the filter list is the following, all of which are in 2 pole and 4 pole low and high pass:
MS1 (Sallen Key MS10)
MS2 (Sallen Key MS20)
SMP (State Variable / Sallen Key blend)
OSR (State Variable OSCar)
SHJ (Cascade OTA SH/Juno blend)
PRD (Transistor Ladder Prodigy)
