The wood-sided CS “M” series appeared in 1979. The CS40M sat in the middle of the lineup, with the monophonic CS20M below and the six-voice CS70M above. Get ready for some synth jargon!
The duophonic CS40 featured two voltage controlled oscillators (VCO), a voltage controlled filter (VCF) with selectable low, high and bandpass filter types, voltage controlled amplifier (VCA), low frequency oscillator (LFO), and attack/decay/sustain/release (ADSR) envelope generators (EG) for VCF and VCA. The EGs featured a 5x switch to increase the envelope time. For real time control there are 36 knobs, 11 faders, pitch bend and mod wheels with selectable destinations and lots of switches. Once you created your sound, you could save it to one of 20 memory locations. If you needed to store more sounds, you could save them to a cassette tape!
Dom Sigalas spent some time with the CS40M at the Berlin Synth Space. Check out his take on the 44-note powerhouse used by bands like Ultravox, Duran Duran and Front 242.