I have another Theremin anecdote which was very special occasion for me. I recorded Miklos Rozsa's Spellbound Concerto in the early 1990s with John Mauceri and the Hollywood Bowl Orchestra. Here's the gloriously lurid CD cover.
What made this recording so poignant and memorable was that the extremely sick composer wanted to attend. We were all very excited in the MGM studio awaiting his arrival, and eventually he was wheeled in by attending nurses. He was barely able to speak a word - just a feeble, painfully-slow mumble - but I remember that he had a beautiful, unlined, noble, kind face. He wanted to sit close to the piano, so they placed him about three feet away where he sat and listened. Unfortunately on that recording we used a synthesizer rather than a real Theremin, with the engineer mixing it on a separate track in the control room, so it could barely be heard in the studio. With great effort, Rozsa kept telling us that he wanted to hear more Theremin until he realized how it was being recorded. If you listen very carefully to the final recording you can hear a quietly murmured "Bravo" from the composer which was not edited out, coming as if from beyond the grave
