The CS-40m is a duophonic (2-voice) analog synthesizer that was introduced in 1979. Although Yamaha had already conquered polyphony with their legendary 8-voice , the CS-40m offered a more affordable approach to something other than a mono-synth. It has a semi-compact 44 note (3 1/2 octave) keyboard, 36 knobs, 12 sliders and over a dozen buttons for easy hands-on performance and editing. This CS-40m is in great working condition with the exception of the programmer, it no longer store patches. All other functions are 100%, and the factory programs can still be recalled to memory. AC power cable included, serial number 1400.