Rita Hayworth performing βPut the Blame on Mameβ written by Allan Roberts and Doris Fisher for the film noir Gilda (1946), directed by Charles Vidor.
There is a rumour that this film is the only time Rita Hayworth's real singing voice is heard, but that is not true. According to the bonus features from the DVD, Hayworth actually never recorded her own singing voice and was a talented lip-syncher. Anita Ellis dubbed almost all of her singing in this film. Hayworth always wanted to do her own singing, and Columbia Pictures chief Harry Cohn paid for her voice lessons, but she never developed a voice he considered strong enough to be used; Hayworth remained bitter about that for the rest of her life.
According to the commentary provided on TCM, although Anita Ellis did voice the big production version of βPut the Blame on Mameβ, Rita Hayworth indeed was singing that song when she is strumming the guitar at the bar.