There was an additive synth, but it wasn't Kurzweil and there was only one model I knew of and saw advertised only once. With 128 sine waves to set, it could do everything but required everything to do something.
There were two (hardware) additives synths, both from Kawai - the K5 and the K5000 series. I have the K5000S, and it is relatively difficult to program.
It sounds like nothing else out there, don't think I'll ever get rid of it.
