The instrument
The Roland D-550 synthesiser module was released in 1987 shortly after the D-50, a 16-voice synthesiser with 61 velocity-sensitive keys. They were the first synthesisers whose sound generation was based on digital, sample-based subtractive synthesis, referred to by Roland as LA synthesis or linear arithmetic synthesis. The two models hardly differ technically, although the D-550 has an improved basic sound and almost 450 adjustable parameters. The external Roland PG-1000 (1987) programmer can be connected for complex sound editing. With the D-10, D-20 and the D-110 rack module, low-cost versions were launched in 1988, followed by the D-70 in 1990.
Alongside the Yamaha DX7 (1983) and the Korg M1 (1988), the D-50 and its counterpart, the D-550, are among the best-selling synthesizers. They have been used by musicians such as Prince, Sting, Michael Jackson, Enya, Jean-Michel Jarre, Tangerine Dream and the Pet Shop Boys.
Details
The sound generation of the D-550 can be divided into the sample section and the synthesis section. It combines an attack sample with the square and sawtooth waveforms of digital oscillators, which provide the sound body (sustain). The samples were recorded with a resolution of 16 bits. The first 47 waveforms are pure attack samples, the next group are loops containing only the upper range of the overtone spectrum and the last 24 samples are sample loops with incorrect loop points. The PCM samples cannot be filtered. The pulse width can be modulated using velocity, aftertouch and LFO. The raw oscillation forms pass through a resonant low-pass filter (Time Variant Filter) with a multi-stage envelope, which can be influenced by an LFO or the envelope responsible for the filter, and then through the amplifier. There are 16 synthesiser voices (tones) consisting of two partials. A partial is a sound chain consisting of an oscillator or sample, including filter, envelopes and LFO. Up to four partials can be combined to form a patch, with seven interconnection options, as well as ring modulation. The D-550 has chorus, reverb and echo effects as well as a 2-band equaliser.