Although her singing was dubbed by Marni Nixon, Audrey Hepburn's singing does actually appear in the form of the first verse of "Just You Wait, Henry Higgins," However, when the song heads into the soprano range (one minute and sixteen seconds in), Nixon takes over vocals.

Does Audrey Hepburn do her own singing in My Fair Lady?

Most of Audrey Hepburn's singing was dubbed by Marni Nixon, despite Hepburn's lengthy vocal preparation for the role.

Did Audrey Hepburn do her own singing in Breakfast at Tiffany's?

When he and Mancini were hired by Paramount to craft a song for Breakfast at Tiffany's, Mercer adapted his lyrics to Mancini's laconic melody. ... Hepburn, who was not known as a singer, performed the song herself, singing sweetly, if sparingly on the track, filling it with romantic yearning for a simpler life.