A Modern Cinderella (1932)

Anita Ragusa, the daughter of a costume company owner, delivers a dress for a costume ball at the last minute. The snobbish customer doesn't like the design at first, but agrees to let Anita model it for her to decide whether to keep it. Charlie, a drunk partygoer, hears Anita singing behind a door. Upon opening it, he sees her in the dress and invites her to attend the festivities. She reluctantly agrees and sings for the other guests.