Breaks my heart, too.  I'd have loved to have heard him sing - my crushing on him most likely would have started there instead of in about January of last year.  I mean, I know he sort of sings in Brokeback, but he does it slightly off-key - I think on purpose.
I'm hopeful he'll do some for-real singing on SNL next week.  Or at least some of his impressions.  Whatever he does, I'm sure it'll be entertaining.