Who dubbed Debbie Reynolds' dubbing of Jean Hagen's singing voice in the movie "Singin' in the Rain?"

Betty Noyes

Yea Mibs. That was the answer I was looking for. After research I found it wasn't quite so simple:
"This merry mix-up of real life dubbing was addressed in Ray Hagen’s article on Jean Hagen in Film Fan Monthly (December 1968): 'In the film, Debbie Reynolds has been hired to re-dub [Jean] Hagen’s dialogue and songs in the latter’s first talking picture. We see the process being done in a shot of Reynolds ... matching her dialogue to Hagen’s and synchronizing it while watching a scene from the film. But the voice that is used to replace Hagen’s shrill, piercing one is not Reynolds’ but Hagen’s own quite lovely natural voice—meaning that Jean Hagen dubs Debbie Reynolds’ dubbing Jean Hagen! To further confuse matters, the voice we hear as Hagen mimes 'Would You?', supposedly supplied by Reynolds, is that of yet a third girl ... [Betty Royce]'. Confusing? Well, there’s more. Although Debbie sang in the movie, notably the title tune (dubbing Hagen!), Debbie herself is dubbed again by Betty Royce in her duet with Gene Kelly 'You Are My Lucky Star.'" (Long, but I just couldn't resisit pasting in the whole story.)
http://www.thecityreview.com/singin.html