Like the Juno series, the JX-3P has 6 voices, but unlike those synths, it has two DCOs per voice, with options to sync DCO 2 to DCO 1, or frequency modulate DCO 1 by DCO 2. Only DCO 2 has pulse width modulation; DCO 1 has three fixed waveforms. Most of the rest of the voice architecture resembles the Junos, with a low pass VCF, a high pass filter, a VCA , an ADSR envelope generator , and an LFO . There are a few additional routing options, such as allowing the envelope generator to be routed to DCO pitch. An onboard sequencer can store up to 128 polyphonic steps, although the editing interface is rather awkward.
Patch memory consists of 32 presets in ROM, plus 32 user writeable patch locations. (There is a hidden third bank of 16 patch locations; see Florian Anwander's page here , which also contains many other tips and tricks for hidden functions.) A cassette interface allows both the user patch memory locations and the sequencer data to be saved and reloaded. The synth has a one-knob interface for patch editing; a silkscreened diagram on the right side of the panel maps parameters to numbers, which are selected by putting the synth into an edit mode and then using the patch select buttons to select a parameter to edit. The diagram actually mimics the layout of the optional PG-200 programmer , which provides a knobby interface. The synth has a keyboard with a five-octave span ; like most early-'80s synths, it is not velocity or aftertouch sensitive. The pitch bend mechanism is a basic version of Roland's pitch stick , which oddly has a maximum range of plus or minus a fifth (7 half steps). Modulation is engaged and disengaged by an on/off pushbutton on the panel.
The JX-3P was the first Roland synth to come from the factory equipped with MIDI. It has some significant limitations; it transmitted and received only on channel 1, and it supported only note on /off, pitch wheel, program change, and sustain pedal messages. Due to CPU limitations, the onboard sequencer does not work when the MIDI interface is enabled, and MIDI and the programmer cannot be used at the same time. Several third party modification kits have been developed that siginificantly expand the JX-3P's capabilities in MIDI and other performance aspects of the synth, including the Inque Organix and the Kiwitechnics Kiwi-3P.
At the time the JX-3P was introduced, Roland put little effort into marketing it since it was competing with the Junos, and the group that designed it was focused on marketing its guitar synths. As a consequence, it did not sell well; the lack of onboard patch editing controls has also been cited as a factor. Estimates on the number produced vary between 1000 and 5000. It is now considered by collectors to be somehting of a hidden gem, usually being priced lower than comparable Juno models. Roland has issued an emulation, the JX-03, as part of its Boutique series of tabletop synths.
The MKS-30 is often touted as being a rackmount version of the JX-3P, but it actually is based on the circuitry of the GR-700 (including the problematic 80017A integrated circuits, which the JX-3P does not use). It has 64 user writeable patch memory locations (no presets), plus 64 on a memory cartridge. The PG-200 programmer also works with it, and it does not have the limitation on using the programmer and MIDI simultaneously. It cannot interchange patches with the JX-3P because it lacks the cassette interface