Vangelis was almost a member of Yes, but they picked Patrick Moraz instead. I liked The Friends Of Mr. Cairo.
Not exactly in the sense that they turned him down, but he wasn't available.
(From his Wiki page which I linked earlier):
"Several months later Vangelis travelled to England to audition with the progressive rock band Yes, after singer Jon Anderson had become a fan of his music and invited Vangelis to replace departing keyboardist Rick Wakeman.
However, after problems with obtaining a work visa and the Musician's Union, and his reluctance to travel and tour, Vangelis declined. The band hired Patrick Moraz,
who used Vangelis's keyboards in his audition."
And to tell the truth I'm glad they did, he was the reason for the first Yes album I ever bought:
Relayer, for "Gates of Delirium".
To get an idea how big a move this was for me, in '76 I was living on a starving student's income and the only other album I bought that year was Jeff Beck's
Wired
I was never a Wakeman fan although my 2 best buddies were huge Yes fans.
In fact one of 'em, a local performing keyboardist, actually got to know Anderson and visited him at his ranch near San Luis Obispo (CA) couple of times.