A lot singers never had the looks, but became pretty famous in their own right and did background vocals, like Anita Kert Ellis, dubbing for
Rita Hayworth.
I always loved Lena Horne. Unfortunately, she rarely did more than "guest spots" in MGM movies. The racist south didn't want to see her so her scenes were cut when shown at southern movie theaters. It's also why she was shut out of Showboat.