The Roland Jupiter-4 (JP-4) was an analog synthesizer manufactured by the Roland Corporation between 1978 and 1981. It was notable as the company's first self-contained polyphonic synthesizer, and for containing digital control of analog circuits (termed "Compuphonic" by Roland), allowing for such features as programmable memories and voice assignment modes.
Priced at US$2,895, it was cheaper than polyphonic machine from its competitors (such as the Sequential Circuits Prophet-5 and the Oberheim OB-X) however it did not sell well in comparison. (These poor fortunes were reversed on the release of its successor model in 1981, the popular Jupiter-8.)
Read more about Roland Jupiter-4: Architecture, Promars, Notable Musicians/bands Known To Have Used The Jupiter-4