The Roland U-20 is a PCM-sample synthesizer, released by Roland in 1989.It was the keyboard version of the U-220 rack module, which was in turn a similar follow-up product to Roland's U-110 rack module of 1988. The U-20 is described by Roland as a 'RS-PCM keyboard', where RS stands for ReSynthesized because the sound-engine can play back a modified version of stored PCM samples. Overview The synthesizer engine itself merely plays back stored PCM samples. Although the U-20 did contain synthesizer parameters like envelopes to control amplitude and pitch, it is not a subtractive synthesizer because it did not include any filter capability. Nevertheless, sample playback can be slightly customized via editing its ADSR envelope and applying DSP effects, like reverb or chorus. A drawback is the absence of filters. The U-20 has standard 64 patches, and can be doubled with an optional RAM-card (the M-256E). There are also two extra slots for ROM PCM-cards to expand the number of available sounds. There's a built-in arpeggiator, a Chord Play feature which plays back a full chord with only one finger, 2 assignable sliders, and the U-20 is compatible with the SN-U110 and SN-MV30-S1 series of soundcards. With one U-20 it's possible to produce a reasonably complete orchestration. The maximum number of voices is then limited by the device itself. The U-20 has given certain Roland-sounds more publicity, like the shakuhachi, the bell, guitar-samples with distortion, and the typical Roland piano-sound, which can be found in later Roland models like the JV and XV series. Editing sounds is limited and relatively complicated due to the small screen and menu layout. Thanks to its popularity, later on there was software made available to edit sounds on a computer via MIDI, or by adding new sounds to the device. There are also hardware presets in programs like Cubase allowing easier communication. U-220 The U-220 is a 1U (19-inch rackmount) module of the U-20. It was the successor of the U-110 that was released in 1988. The U-220 has the same LCD screen and expansion possibilities, but fewer knobs on the front panel than the U-20. Features 128 different voices (additional may be supplied with ROM/RAM cards) Programmable DSP unit offers reverb, delay, chorus 3 demo songs 61 keys with note velocity and aftertouch abilities MIDI In/Out/Thru DIN connectors Phones output, Mix Output (L/R) and Direct Output (L/R) jacks Pedal switch and Expression pedal