Voltage control synthesizer   

the “classic” patch: 

 The voltage control synthesizer comprises a set of signal sources and signal processors (modules) configured to make a variety of timbres.  The phrase voltage control refers to  the modules having many of their parameters controllable by either a potentiometer or via a direct current voltage. This feature enabled complex new timbres to be created by "patching" signals or control voltages from one module to another.  Thus one could have one oscillator modulating the frequency of another (FM) or perhaps the amplitude of an amplifier (AM). The different modules may be user - configurable or fixed by the manufacturer in how they are interconnected.  The "classic" patch was a standard configuration found in a variety of synthesizers because it offered (a) a wide range of timbral possibilities and was fairly simple to understand and (b) it could be used for conventional instrumental imitations.  This patch is the basis for many contemporary synthesizer signal path concepts.
"Putney" (VCS-3)  voltage control synthesizer, circa 1970, designed by Peter Zinovieff.  Uses small pins to connect various modules via an ingenious x/y matrix. Modules left to right from the top: oscillator 1/ring modulator/low pass filter -
oscillator 2/envelope generator - oscillator 3 (low frequency)/reverb - noise generator/output filters/levels for external input/meter - pin patch/joystick/output levels. Not pictured, four octave keyboard (The Cricklewood")