The GX-1 was designed, with strong chrome legs supporting a white console. The main unit housed three keyboards - two full-sized velocity-sensitive manuals (5-octave 61-note keyboards), and a shorter but full-width monophonic pressure-sensitive manual (3-octave 37-note keyboard), a 25-note pedalboard, a 'relative' ribbon controller (zero modulation was wherever you placed your finger first. Selected parameters could be affected by velocity, aftertouch pressure, and key motion. The modulation value rose and fell as you moved your finger left and right), two 'swell' pedals and a springloaded knee controller. The GX-1 contains several polyphonic analog synthesizers, and it incorporates features for home organists and the professional rock/pop musician. Beside the great sonic possibilities of the synthesizer, the keyboards allowed levels of touch control never before seen.
It had at least eight voices, plus one monophonic voice. Each poly voice had two analogue 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, to program, store, and recall sounds. Beneath are a set of bass pedals similar to any home organ.
The GX-1 was an early design that would eventually evolve into the more commercial Yamaha CS-80 synthesizer. As powerful as the GX1 was, it was still very expensive, so few musicians were able to afford it. The GX-1 cost US$60,000, and was premiered in the US in 1973 at the NAMM convention. Fewer than 100 GX-1s were made. The console weighed 300 kg. The pedalboard and stand add 87 kg, and each of its valve-powered loudspeakers weighed 141kg.
Stevie Wonder made use of it early on and called it 'The Dream Machine'. During his Songs in the Key of Life album, he demonstrates it especially well on the tracks 'Village Ghetto Land' and 'Pastime Paradise', where he creates an animated string section. Keith Emerson also used the GX1, initially on ELP's Works Vol. 1 album, on 'Pirates' and 'Fanfare for the Common Man'. It is also featured on their 1979 Live album on the opening track, 'Peter Gunn'. Benny Andersson of ABBA, also kept one at Polar Studios, in Stockholm, Sweden.
John Paul Jones bought his GX1 around the time of the In Through the Out Door sessions in late 1978. The album was recorded in Sweden at Polar Studios. Benny Andersson, ABBA's keyboardist, may have influenced this purchase, since he was one of the few GX1 owners at the time. It can be heard on 'In the Evening', 'Carouselambra', 'All My Love', and 'I'm Gonna Crawl'. On the final Led Zeppelin tours (1979-1980), Jones used the GX1 as his main keyboard. He would perform organ, clavinet, bass, and synthesizer parts with it. Although it was an improvement on the Mellotron, he later sold the GX1 to Keith Emerson as a spare. Many other keyboards by then could replicate its sound.