The instrument
Yamaha offered eight new analog, monophonic synthesizers of the CS series in 1977-1979: CS-5, CS-10, CS-15, CS-20M, CS-30, CS-30L, CS-30D and CS-40M. They follow on from the company's first synthesizers SY-1 and SY-2. The CS devices offer similarities, but have individual components and tonal differences. The CS-20m is equipped with dual VCOs that use subtractive synthesis to produce bass, synth, lead, bubbly squirty and percussion sounds.
Details
The CS-20M has the essential components of a classic synthesizer: a resonant filter with switchable high-pass, band-pass or low-pass filtering and its own ADSR envelope controls, an ADSR VCA envelope generator with a third oscillator that generates a sine wave and an LFO to modulate PWM sweep. It has 8 memory locations, more than any other CS synth.