A polyphonic digital synthesizer released by Roland in 1991. Since the mid-1980s, Roland, like most of the industry, had been moving towards products with minimal user interfaces, generally of the type where the performer, in order to edit patch parameters, had to first select a parameter by scrolling through a list presented on a small LCD display, and then use the synth's single data entry wheel or slider to change the value. These one-knob user interfaces lowered the cost of producing the synths, but also deprived the performer of the immediacy of being able to edit patch parameters on the fly. In the days prior to computer-based editing, Roland's method of solving this problem, for the community of perfomers who were concerned about it, was to offer the PG series of programming panels that provided a set of parameter knobs and sliders, and connected to the synth through either a proprietary bus or MIDI.

With the JD-800, Roland in effect took the PG programmer and built it into the synth, creating one of the first digital synths with an extensive, real-time-tweakable user interface. The voice architecture was fairly basic, starting with a digital oscillator using a combination of wavetables, attack transients, and percussion sounds. A digital filter("TVF" in Rolandese), selectable between lowpass, bandpass, and high pass, and capable of some quite nasty resonance, was followed by a digital amplifer (the "TVA"). Each of the oscillator, TVF, and TVA, had its own complex envelope generator, and there were two LFOs with a number of choices of waveform and offset. Extensive routing options were provided for the LFO signals, as well as velocity and aftertouch. Onboard effects were also provided; these did not have knobs on the panel and had to be set up using menus.

The synth allowed up to four voices, with different patch settings, to be layered in each patch. Doing so took additional voices, however, which decreased the polyphony; 24 voices were available. The synth was also multitimbral, although the selection of onboard effects available in multitimbral mode was limited. An interesting feature in the multitimbral mode was the "special part", which allowed a different single-layer patch to be assigned to each note on the keyboard.

Despite it being the type of digital synth that everyone said they wanted, the JD-800 did not sell well at the time. This didn't stop Roland from following it up with the JD-990 rackmount version. The 990 corrected a couple of the 800's problems, providing a ring modulation mode that was missing from the 800, and adding DSP capability so that the full range of effects was available in multitimbral mode. The 800 served as the programmer for the 990; with the proper MIDI linkup, most of the 800's controls could edit the corresponding parameter on the 990.

Both synths provided memory card slots which could be used to load additional waveforms, and plug in memory cards for additional patch storage. The 990 also provided an internal slot for an expansion board which would provide both additionl waveforms and patches using those waveforms.

The JD-800 and 990 are now both highly regarded by performers and collectors. However, many 800s have experienced keyboard failures due to something called the "red glue" problem; a glue that Roland used to attach weights to the underside of the keys turned deteriorated over time and ran over the underside of the key bed, causing keys to stop working. Roland at one time was selling replacement keyboard assemblies, but they are now out of stock and no longer available. It is possible to clean up the red glue and restore the keyboard using various mixtures of noxious chemicals.

Community content is available under CC-BY-SA unless otherwise noted.