The GX-1 [along with it's predecesor, the "Electone GX-707"] was an analog polyphonic synthesizer developed by Yamaha as a test bed for later consumer synths. With its chrome pedestals and curved metallic body, it looked like a 23rd-century version of the Hammond B3. The GX-1 had two full-sized velocity-sensitive manuals [5-octave 61-note (C-C) keyboards], a small monophonic pressure-sensitive manual [3/4 scale, 3-octave 37-note (C-C) keyboard], a 25-note pedalboard, a neat "relative" ribbon controller [zero modulation was wherever you placed your finger first. The modulation value rose and fell as you moved your finger left and right], two "swell" pedals and a springloaded knee controller. It had at least eight voices, plus one monophonic voice. Each poly voice had two analog voltage-controlled oscillators, a 2-pole low-pass filter, at least one (poly-mod) voltage-controlled low-frequency oscillator, and at least two envelope generators. The different keyboard's voices could be coupled together like an organ (there are "stop" pistons between manuals), so that sounds could be layered. The monophonic voice could also be layered onto the polyphonic voices, as the top note. The synth was programmed via a bunch of miniature sets of controls hidden in drawers and panels on the instrument. There were also rows of Yamaha 'drawbar' sliders and some buttons above the middle manual.
The GX-1 cost $60,000, and was premiered in the US in 1973 at the NAMM convention. At least seven were built. One was displayed for a time at Leuenberger's in San Francisco. Keith Emerson, John Paul Jones of Led Zeppelin, Jurgen Fritz of Triumvirat, and Stevie Wonder all bought one. Stevie Wonder called it "The Dream Machine." You can hear the gorgeously expressive string sounds that it was capable of on Stevie's "Village Ghetto Land" and "The Secret Life of Plants." Jurgen Fritz used his on the Triumvirat album "Pompeii." ----Jim Smith
In 1977, Yamaha unveiled the CS-80 which has the same circuits that GX-1 has as ICs.
Benny Andersson of Abba - quoted as saying, "It has no limits, that machine",
Chess - the musical (London production),
Keith Emerson - on "Works" and almost exclusively on "Fanfare for the Common Man",
Juergen Fritz of Triumvirat,
John Paul Jones of Led Zeppelin - used extensively on "In Through the Out Door" (this instrument was later sold to Keith Emerson),
Mickie Most of Rak Studios and Hot Chocolate,
Rick van der Linden,
Stevie Wonder - on "Songs in the Key of Life" and "Journey Through the Secret Life of Plants",
Hans Zimmer - who bought Keith Emerson's GX-1
[Let us know if you have any further additions to this list.]