
Title link takes you to an April 1977 article in Synapse Magazine that mentions a "prototype of a large complex polyphonic system, as yet unnamed, that will begin production this summer. It will list for around $6500." There is also mention of other products like the MOOG Polymoog, Steiner-Parker "Synthasystem," ARP, KORG and more. It's a great read if you like going back in time.
You can find the January 1979 review of the Yamaha CS80 in Synapse
here.
You can find more issues of Synapse scanned on
Cyndustries under the Goodies section.