The VCS3 has three oscillators (in reality, the first 2 oscillators are normal oscillators and the 3rd an LFO or Low Frequency Oscillator), a noise generator, two input amplifiers, a ring modulator, a 18dB/octave (pre-1974) or 24dB/octave (after 1974) voltage controlled low pass filter (VCF), a trapezoid envelope generator, joy-stick controller, voltage controlled spring reverb unit and 2 stereo output amplifiers.
The VCS3 was quite popular among progressive rock bands and was used on recordings by The Alan Parsons Project, Jean Michel Jarre, Hawkwind, Brian Eno (with Roxy Music), King Crimson, The Who, Gong, and Pink Floyd, among many others.
Well-known examples of its use are on The Who track "Won't Get Fooled Again" (as an external sound processor, in this case with Pete Townshend running the signal of a Lowrey Organ through the VCS3's filter and low frequency oscillators) on Who's Next.
Although the VCS3 is often used for generating sound effects due to lack of built-in keyboard, there were external keyboard controllers for melodic play.
Unlike most modular synthesizer systems which use cables to link components together, the VCS3 uses a distinctive patch board matrix into which pins are inserted in order to connect its components together.