On the comment section, Richard David James (under the name of user18081971) mentions that he used the Yamaha GX-1 for a few tracks. "i did quite a few with it, looking very forward to having it fully midified. Trouble is though id rather Colin make more o.s updates to Cirklon!"

Jones states in this interview that he used a Yamaha GX-1 with Led Zeppelin and then sold it to Keith Emerson.

In the case of 'Pastime Paradise', a Yamaha GX1 served as the starting point. A huge and powerful polyphonic analogue synthesizer, with chrome pedestals and a curved metallic body, the GX1 — introduced in 1973 as a forerunner to the CS80 — housed three keyboards, a pedal-board, a ribbon controller that produced modulation changes, two swell pedals and a spring-loaded knee controller, along with a variety of buttons and switches to program, store and recall sounds. The top three-quarter-scale, three-octave, 37-note keyboard had half-size keys and offered unprecedented touch control; the other two five-octave, 61-note standard-size keyboards were equally functional, with horizontal position control enabling the player to achieve effects such as vibrato by moving the keys side-to-side.

This Sound On Sound article states that Emerson used a Yamaha GX-1.

"There had been the Yamaha GX1 before that, which Emmo and Stevie Wonder had got, which was supposed to be worth over twice that, but I don't know if they ever paid for them or whether they got them on some sort of endorsement deal. It was funny, when we were in Japan a few years ago - we saw quite a few of them stuck in resorts and hotels and places like that."

At 2:06, it appears that Minoru appears to have a Yamaha GX-1 on his right side. It's really chunky and has the three tiers of keys so it would appear to be a GX-1.

One of the last GX-1s manufactured was the one acquired by Benny Andersson in early 1979. This particular instrument was from then on used on many of the songs that were recorded by ABBA during 1979-1982, on the album musical “Chess” from 1983-1984 as well as on numerous other recordings from that era. It has also toured the world with ABBA in 1979 as well as being used on the concert version of “Chess” in 1984.

In the liner notes of the New Triumvirat album "Pompeii," Jürgen Fritz is credited with playing the Yamaha GX-1, as documented on Discogs.

Rick van der Linden's solo album GX1 was played entirely on a Yamaha GX-1.

video of Firechild performing on the Yamaha GX-1 in his studio