"In the Pittsburgh Post-Gazette of November 20, 1963, “At Random" columnist Harold V. Cohen wrote that Hepburn's vocal coach, Sue Seiger Seton, praised her highly and said that she “will be a revelation." But he told his readers that Frederick Loewe had told him this: “Forget it. Audrey won't sing a note. She'll be a wonderful Eliza. I've seen some of the rushes, but the numbers will be dubbed in for her by somebody else." Cohen then wrote that Jack L. Warner insisted to him a couple of days later that “Audrey will do every song herself."
I fully understand Loewe not wanting both of the leads in the film to be talk-singers, or non-singers, but I wish the version of Wouldn't It Be Loverly? that Audrey recorded had been left in the film. I actually find it charming. I suppose it isn't legal to post a link to it, but it can be found on YouTube. I also prefer the version of Just You Wait without Marni singing in the middle. The King sang so much of the section in the film anyway that Marni's voice wasn't necessary. Otherwise, I think the decision to dub was essential to the film's success and is quite well handled in The Rain In Spain (with Audrey speaking and Marni singing) and I Could Have Danced All Night, with Audrey singing just a bit of the intro.