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 are 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. The concept of “Control Voltage” is one of the basic principles Bob Moog used to control sound and create his groundbreaking electronic instruments. Moog Controllers modify, mix, and distribute control voltages to produce the incredible variety of sounds and effects that analog synthesizers are famous for.