“The Korg FK Series pedals date from the early 70s [I’m not sure about that. Era seems more late 70s to me?] and includes several models from Envelope Filters, Wah, Phasers, Modulation, Expression, Control Voltage, Etc.”
“The vintage Korg Mr. Multi FK-2 is a multi-effect pedal with phaser, single wah, double wah, and envelope filter when switched to “auto”.
Discussion on this effect can be found here.