Supposedly it was Warren Beatty.
One of the best concerts I ever went to was SUPPOSED to be a "James Taylor Concert"...but Carly Simon was there with him and did HER thing...and they both additionally did a few duets...and the gal on piano was Carole King, and she did her thing, too! GREAT CONCERT! The concert was In Little Rock, AR in the fall of 1971.
Ugh, let me see if I can come up with something again. Here's one I don't know the answer to but your question reminded me of it. Who was Carly Simons "You're so vain" about. At one time I thought it was James Taylor but I really don't think that's who she was referring to.
I just thought of one I actually do know. Who was Bob Seger referring to in "Her Strut"?