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 employing digital control of analog circuits (termed compuphonic by Roland), allowing for such features as programmable memory, voice assignment modes, an arpeggiator, polyphonic portamento and others. Priced at US$2,895, it was dramatically cheaper than other polyphonic machines from its competitors (such as the Yamaha CS-80, Korg PS-3300 Prophet-5 and OB-X). While it didn't sell as many units compared to the competition, its primary design was such that it could be an accompaniment to organs, complete with an option for a music sheet stand to be fitted. Its future successor in 1981, the Jupiter-8, would go on to sell many more units and make Jupiter a recognized brand. Architecture The Jupiter-4's basic architecture consisted of four voice cards (usually identical, unless mismatched revisions were installed by repair shops), each containing a: VCO, sub-oscillator, VCF (resonant low-pass which can self-oscillate), and a VCA. Early revision voice cards feature four discreet BA662s, while later revisions feature a single IR3109. Modulation included an attack-decay-sustain-release (ADSR) envelope for the filter, and another for the voltage-control amplifier and a final level output with an overload LED, as well as a separate unmemorized master volume control. In typical Roland fashion, the filter ADSR could be inverted allowing for "upside down" modulation. The LFO was notable for being able to reach audio frequencies, allowing for crude FM and AM synthesis. The LFO is routable to a comprehensive amount of options, including: the bender, VCO pitch, pulse-width, both highpass and lowpass filter cutoff, and the VCA. The final VCA level setting could be memorized in user presets, and was prior to the overall master stereo output volume. Those settings were memorized in the user presets but a fully adjustable depth remained independently configurable through the pitch wheel to combinations of VCO, VCF and VCA, as well as a bend range. The VCOs can garner unstable tuning if aging or low-quality electrolytic capacitors are used (two for each voice card). Synthesizer repair shops can replace these tuning capacitors with stable polystyrene capacitors for an instant perfect tune. Individual oscillator card VCO tuning is accessed by four capped holes in the middle of the back of the case, but the unit should be allowed to warm up before adjusting for at least