Christopher Plummer's Odd Performance in The Sound of Music

Those stories are grossly exaggerated.

As Oy! stated, Hepburn knew very well that she was going to be dubbed, but she DID want to try to at least sing “Wouldn’t It Be Loverly” on her own. She was lead to believe this would be the case, and she was working very hard with a voice coach and even recorded her version of it, and was told it would be in the film. Eventually, she was told that Nixon would be doing that song as well, and hurt and betrayed, she walked off the set.

The next day, Hepburn came back, very meek and appologized for her behavior.
As for Nixon and Andrews getting together to dis Audrey-I don’t think so. Audrey never EVER had a rep as someone who threw tantrums on the set-in fact, she’s well known for being a kind and gracious person. And both Hepburn AND Andrews deny any animosity over the role. They were known to be quite friendly with one another, and consider that Andrews was married to Blake Edwards-who had directed Audrey in Breakfast at Tiffanys.

And no, Audrey was never going to be as good as Andrews. BUT, I do prefer her version of “Loverly”* to Nixon’s, as Nixon’s was far too polished and pretty for the guttersnipe flowergirl Eliza. She also didn’t sing with an accent, as Hepburn DID. So I think while Nixon’s was technically better, Audrey’s had more character.

And Audrey could INDEED sing-rent yourself Breakfast at Tiffanys. Forget Andy Williams-NO ONE else can do “Moon River” justice.

*When the DVD of MFL was released, Hepburn’s version was restored to the closing credits, IIRC.

We now end this Hijack and return you to your original topic.

Some googling indicates that you are correct.

Indeed:

Audrey Hepburn sings Moon River.

(There is a clip of the scene from the movie at youtube, but this one is a nice edit with scenes from the movie)

Moon River was written expressly to fit her somewhat limited range. "Mercer and Mancini originally wrote the song for Hepburn to fit the actress’ limited vocal range (Hepburn was not an accomplished nor an established singer). " from Wikipedia.