Casio • VZ-1 / VZ-10M

The VZ-1 is a full-sized, 5-octave, velocity & pressure sensitive keyboard utilizing the IPD tone generation (a type of Phase Distortion synthesis) and offers 16 note polyphony. It's a digital synth capable of some great strings and "polite 80's sounds". You could use up to four sounds for splits, layers, velocity, cross-fades, etc. It has a large, blue, back-lit LCD display for editing patches. Editing is in-depth and quite a different approach than other synths before it. Its sounds are akin to the Casio CZ-series and sort of Yamaha DX-like. It's not particularly cool, but it looked impressive in its day with the blue back-lit graphical display.

The Casio VZ-10M is a rack mount version of the VZ-1.
Another thing with J:s comment -it's not thinner than DX/TX synths its just different if not "fatter".
It depends programmiing skills and effort. Envelopes are in big role with this machines and because those are 8-stage it asks time.. especially with VZ8M version which has no any data slider and everything is edited through button presses.
I also had Hohner HS2 for a while so i know what difference it makes. HS2 is VZ1 with different name and look BTW. I wish that someone somewhere would make hardware controller for this iPD synths.. :P
If you have one of this iPD synths and are unable to program it find a manual.
It's freely available as PDF.
Anyhow this iPD is possibly the most difficult synthesis to learn. :)