Roland D-20

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The Roland D-50 is a polyphonic 61-key synthesizer produced by Roland and released in 1987. Its features include Linear Arithmetic synthesis, on-board effects, a joystick for data manipulation, and an analogue synthesis-styled layout design. The external Roland PG-1000 (1987-1990) programmer could also be attached to the D-50 for more complex manipulation of its sounds. It was also produced in a rack-mount variant design, the D-550 (1987-1990), with almost 450 user-adjustable parameters.

The D-50's capabilities could be modified through the addition of third-party products by Musitronics, most notably the M-EX which made the D-50 multitimbral (the D-50 was bi-timbral), as well as a chip that improved the D-50's response to incoming MIDI commands and a system for burning custom PCM cards with user samples for playback in the D-50.

Although the D-50 was among the first non-sampling machines to be able to produce sounds with sample-based characteristics, it was not long before many synthesizers on the market began using similar methods to create sounds. Roland later released a series of lower-priced keyboards and modules that allowed musicians who couldn't afford the relatively expensive flagship D-50 to have some of these sounds (Roland D-10 (1988), D-110 (rack version of D-10) (1988) D-20 (1988), D-5 (1989), MT-32). Though these lower priced D-series synthesizers did not contain the full "LA" synth engine, each was 8 part multi-timbral, and Roland doubled the number of onboard PCM samples. Roland also produced the 76-key, 6-octave "Super-LA" D-70 (1989-1990). With the D-70 Roland removed the digital synthesis section, which was replaced with full-length, more realistic and natural sounding samples, including an acoustic piano, which the D-50 lacked. The D-70 also had an expanded filter and effects section and was 5 part multi-timbral. Even with its improvements, however, the D-70 was unable to catch up with the dominant workstation of the time—the Korg M1—and failed to become the next Roland flagship synthesizer.

The D-50 produces a hybrid "analog/digital" sound: one can use traditional fat analog waveforms like saw and square (digitally created on the fly unlike competing synths of the time that used PCM samples of waveforms, ala Korg DW-8000) together with PCM samples of actual acoustic instrument attack transients and famous analog synths of the past, filtered through full analog-style processing (LFOs, TVFs, TVAs, ring modulator, effects, etc.). This breakthrough led to the creation of totally new sounds never done before on either pure analog synths or samplers.

Each D-50 sound ("patch") was made up of 2 "tones" (Upper and Lower) and each tone was made up of 2 "partials". Each partial could be either a "synth waveform" (pulse or sawtooth waveform) and a TVF (time-variant filter, the digital equivalent of a VCF) or a digital PCM waveform (sampled attack transient or looped sustain waveform). The partials could be arranged following 1 of 7 possible "structures" (algorithms), with a combination of either a PCM waveform or synthesized waveform, with an option to ring-modulate the two partials together. The synthesized waveforms could be pulse-width modulated and passed through a digital 4-stage Low-Pass filter, allowing for subtractive synthesis. The lower and upper part could be split or played in dual on the keyboard. The dual configuration allows an 8-voice polyphony bi-timbrality while only one partial plays, which allows for 32 voices.

Not only was the synthesis method new; the D-50 was arguably the first commercial synthesizer to include digital effects such as chorus and reverb, adding to the characteristically bright, rich, lively and sometimes realistic sound, featured on countless records of the period. Each of those effects had 10+ variations with editable parameters usually found in dedicated rack effects processors rather than keyboard synths. It was also on the forefront of the change of the look of a typical keyboard player on stage: instead of being surrounded with multiple instruments, with more versatile instruments and the continued adoption of the MIDI standard, they were starting to appear with only one or two keyboards, typically a D-50 with either Yamaha DX7 or Korg M1.

The D-50 was fully MIDI-compatible, though it transmits on only one channel. The keyboard was velocity- and after-touch-sensitive, and the keys were slightly "weighted" with metal for a higher-quality feel. It included 64 patches on-board, and 64 more patches were available on the expansion RAM card that was included. It uses a CR2032 lithium battery for memory backup.

For its sound and build quality, and the unique synthesis method it featured, the D-50 has remained popular to this day. Its synthesis engine, in more or less updated forms, was used in Roland's JV and XP series synths, among others. Furthermore, in 2004, Roland released a VC-1 expansion card for V-Synth and VariOS synthesizers. It contained a modeled and updated D-50 synthesis engine and the original operating system, including factory- and all Roland "expansion cards" patches. Since newer DAC chips sounded different (cleaner), it included the option to simulate the D-50's "rougher" output.

The D-550 is a rack-mount version of D-50, with fewer front panel controls, no joystick and sliders. It employs the same sound circuitry (the main circuit board is exactly the same in both, labeled "D-50/D-550")