The SCI Prophet VS uses 4 digital oscillators per voice (127 waveforms) and 4 pole LP analog filters. Big possibilities, instead of lack of a great interface. “Vector synthesis” at its best !
Not an analog beauty here but an obscure vintage keyboards series made by Seiko in 80’s. The Seiko DS-202 keyboard is a simple home arranger (tones + rhythm + bass chord system) with a great analog chorus but an interesting thing here is that sounds generated are not made from subtractive, FM or PCM synthesis but from additive synthesis. And the Seiko DS-310 synthesizer module offers the possibility to fully edit it!
To finish, the Seiko DS-320 module is a sequencer, since the DS202 doesn’t have MIDI ports (you will have to get the Seiko DS-250 for MIDI capabilities, and to oscillator layers instead of one but no more rhythms or bass chords).
Anyway, since hardware additive synthesizers are rare and expensive (RMI Harmonic Synthesizer, Digital Keyboards Synergy, Fairlight CMI, Synclavier, Kurzweil K150, Kawai K5x-serie), it may be worth trying this great vintage and cheap synth for unique pads, atmos, choirs and strange FX…