Just a minor note here, Shadowgram reports that Mame is David Selby's "first musical performance."
He has appeared in a few musicals before, including Brigadoon and Oklahoma in Morgantown, West Virginia in the early 1960s.
However, this may very well be the first time he's had to sing a solo part. I am not familiar enough with the musicals mentioned above to know just what the characters Sandy Dean and Will Parker do or don't sing in them.