I read that old thread, what a flashback! I'm still here, wow.

I thought the thread had addressed all of that, but I guess not - to recap, and a lot of this has been posted before but just to update it.
Mike played the Moog Ribbon Controller live for the first time at the Michigan shows. It was to the best of my knowledge the first time that device had been played onstage anywhere. Robert Moog had been building replica Theremins (his company Big Briar still builds them) because the original RCA (and other) cabinet models were scarce even in the 60's, and there was a demand.
So the Beach Boys approached Moog sales rep for the East coast named Walter Seer (who currently owns and runs Seer Sound, an incredible vintage-leaning studio) wanting to buy an actual Theremin to take on the road. Good Vibrations was the catalyst - they needed it to play the song live. So Walter Seer has a demo of an actual Theremin built by Moog, but no one could play it, and it would be all but uncontrollable by a non-skilled player on stage, especially at a pop concert. So Moog himself set out to build something that *could* be played, was reliable and easy to manage, and would stay in tune.
Paul Tanner was specifically asked to tour with the Beach Boys in '66, just to play Good Vibrations, but he turned them down. That's what led them to Seer's shop.
That was the Ribbon Controller - built specifically for and at the request of the Beach Boys to play Good Vibrations live in 1966. The ribbon controller later became an integral part of the earlier Moog modular synths, and there are still examples of them sitting just above the actual keyboard if you get to see an old Moog from the late 60's The Beatles made it popular as well - George Harrison had bought one in Los Angeles when he was spending time out there, most likely from Moog's West Coast rep, Paul Beaver. Paul Beaver was the same Moog guy who had pitched the then-new instrument at the Monterey Pop festival in summer '67, and who sold one to Micky Dolenz. Then Dolenz a few months later played the first Moog part on a pop record on the Monkees "Pisces Aquarius..." album, on the track Daily Nightly, but the instrument was at that time so complex they needed Beaver at the studio to set it up. Paul Beaver himself played that same Moog on the song Star Collector after they needed a more specific part than Dolenz at that time could play.
Harrison's Moog from L.A. is the one that's on several prominent Abbey Road tracks, and they specifically used the ribbon controller - thanks to the Beach Boys' need for it a few years prior - on "Maxwell's Silver Hammer" and a few other swooping synth leads on the album.
As for Paul Beaver - I remember Stephen Desper posting a few stories about going to seminars/classes that Paul Beaver was holding in California on music synthesis and engineering. It was fascinating stuff, I just can't recall where those stories could be found now. He's one of the heroes of early synthesizers in popular music.
And coming full circle, the Theremin played by Paul Tanner on those studio sessions like Good Vibrations was made specifically so Tanner could play the notes precise and in tune consistently, a trait the original Theremin did not have and which only an elite club of players ever mastered through the years, Clara Rockmore being perhaps the best of all time.
I can't confirm this, but I'm assuming Moog's eventual design of the Ribbon Controller for the Beach Boys borrowed the concept of having a flat, keyboard-style layout on which to slide into the notes and have them in tune, from Tanner's Electro-Theremin design. That was the proven success and what gave Tanner a boatload of studio work - not only could he play it in tune, but he could read charts which an arranger would write for the instrument, which opened up a lot in the way the Theremin could be used in an orchestration.
If you add it up, Tanner and the Theremin were a natural fit: Tanner was a trombone player, and like the Theremin, there were no keys, frets, or specific "notes" on the trombone...you would slide into the note based on position, just like the Theremin-Tannerin-Ribbon Controller.