Who sang in this movie?

I have seen and always admired Isabel Jewell, who brightened many a movie in the 1930s and 1940s, my favourite Jewell role being "A Tale of Two Cities". But never have I seen her as glamourous as in "Shadow of Doubt". However, I have never read of her having singing talents.
It was often the custom in the 1930s to dub actors when a song was required and so I am guessing that Jewell may have been dubbed in this movie. Does anyone have any information to confirm or not, and if she was dubbed who the actual singer with the beautiful voice was? Thanks!
This is a very entertaining light mystery with comedy elements. The bantering relationship between Collier and Brophy is reminiscent of that between Edna May Oliver and James Gleason in RKO's Hildegarde Withers mystery films. Recommended.