Okay, here's one: The Band Leader from Big Bird Leads the Band. I joined Rdio.com, which has tons of albums for free listening, including most of the Sesame titles, and it's been a useful resource. The voice is David Korr (given joke billing), but on the cover photo?
I actually think it looks rather like Caroll Spinney, and for a photo they could have had a stand-in inside Big Bird, but it's a resemblance (and whiter beard and hair then he would have had in 1977), not a certainty. And it could be somebody else from the crew (or just nobody we know at all). Thought I'd toss it out there anyway.
Yeah, I knew this might be tricky to answer, but I thought it would be a good use of the forums to park the info. *Possibly* there may be something in the Maryland CTW Archives in some folder (given that most of what we *did* uncover, outside of the Margaret Hamilton appearance or "Muppet Fear," was often random) or which some of the folks Joe's had contact with, who sifted through so much for the 40th anniversary book and materials, might be able to answer.