Margo:
I don't really believe Prince was incorrect. He wasn't saying that LOVEMUSIK was the first musical at the Biltmore, but (and this is just my opinion) I believe that by saying "staged in the house", he meant really done from scratch in that exact theatre. And by that definition, he's not really wrong...LOVEMUSIK is really (I think) the first original to be "born" there.
HAIR (correct me if I'm wrong) was at the Public originally.
STARDUST was originally done at Theatre Off Park
THE ROBBER BRIDEGROOM was originally done at The Acting Company.
DOONESBURY was of course based on the comic strip, but I don't know anything more about it's original production.
"If you are going to do something, do it well. And leave something witchy."
-Charlie Manson