She did not know going into production that the majority of her singing was to be dubbed, but she was well aware that she could not do it all. I believe her understanding had been that she would record all of the songs to the best of her ability, that Marni Nixon would also record the songs, that they would be filmed with Audrey lip-synching to both her own and Marni’s playback and that a decision would then be made as to which versions or combinations of versions to use. She was told after a couple of her numbers were shot that they were primarily going with Marni. She angrily left the set and returned the next day, apologized for her rudeness and got on with the shoot.
She may have been contractually obligated to not discuss her dubbing with the press, though there is footage of her at the film’s premiere acknowledging the work it took to make two voices seem as one.
She also, many years later, could not remember Marni Nixon’s name in a Larry King interview, but described her as a “lovely girl.”