
via this auction
"The CP-251 Control Processor can be used in connection with one or more Moogerfooger analog effects modules, the Minimoog Voyager, or other voltage-controlled gear. The CP-251 adds the same kind of power and versatility of the classic MOOG modular synthesizers.
There are two kinds of signals in a modular analog synthesizer: audio and control. As audio signals go through a system of synthesizer modules, they get shaped into the sounds that you hear. Control signals, on the other hand, correspond to the variations in the sound that are imparted by the synthesizer modules, like invisible hands that turn the knobs of the modules.

