The D-20 makes a great budget or alternative D-50. It's more closely related to the D-10 and D-110 synthesizers but adds an 8-voice sequencer with a rhythm track. The D-20 is a digital synth that employs linear arithmetic synthesis (LAS). It's a confusing synthesis / editing method composed of tones, partials and timbres. Basically it all boils down to tricky programming which, if you know what you are doing, can have interesting and unique results. Reverb effects and internal / external memory storage are also available on the D-20. Definitely worth a listen.
Demos & Media
Roland D20 demos part1
Roland D20 demo part2
Polyphony - 32 voices
Oscillators - Digital LAS (Linear Arithmetic Synthesis) & ROM Samples
Effects - 8 Effects
Multitimbral - 9 parts
Drums - 1 kit, 63 sounds
Memory - 128 preset patches, 64 user patches 128 performances
Keyboard - 61 keys with velocity
Control - MIDI
Date Produced - 1988
Websites of Interest
Images from Perfect Circuit Audio.