That would be a Yamaha TX-816 Chas...essentially 8 DX-7's (or TX-7) in a rack mount unit.

http://www.sonicstate.com/synth/yamaha_tx816/

Awesome sound...there was a piano patch available that used each module for a part of the piano sound, one for hammer thunk, another for string resonance etc...it was pretty convincing back in the day.

Ian
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.