reverb.com - Though lesser known and exceedingly rare (we've only ever had one other listed on the site), the Oberheim Voltage Controlled Filter was used by Frank Zappa in a number of
Doepfer A-106-6 XP Eurorack Filter Module (Oberheim Expander) - Signal Sounds
Tom Oberheim SEM with MIDI to CV Converter — Eurorack and Modular in Asia and the USA