Available as an assembled Module and as a DIY project.
This Module is currently available.
vactrol based filter
the VCF2 is leaned on the A101-1 schematics by the godfather Dieter.
a bit like the LP section of the good old MS20 filter. (12db filter slope)
if you crank up the resonance it could distort quite heavy and make every synth scream like an E-guitar.
Doepfer A-121 VCF2 Multimode Filter
Random Source Serge Variable Bandwidth
Doepfer A-121-2 VCF 12dB Multimode
Erica Synths Black Polivoks VCF V2
Erica Synths Black Polivoks VCF V2
Erica Synths Black Polivoks VCF V2