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In addition to mirko's writeup:

Unfortunatelly Quasimidi are no longer in business and their websites only contain an error message in German (for the .de site) and a place holder porn ad (for the .com site)

Quasimidi's products often got a mixed reception when they were launched: you either hated or loved them. They went their own way with just about everything (with the possible exception of the rave-o-lution) and some of the amazing features was almost impossible to get to work due to the less than intuitive user interfaces.

If you want something that doesn't sound exactly like the Rolands, Korgs and Yamahas everybody else use, you might still want to try out a Quasimidi synth if you get your hands on it. Personally, I use their Quasimidi Cyber 6 midi controller keyboard (basically a Raven without the sound generators) and love it!