Rainbow Over Broadway (1933)

Producer Don Hayes wants to help song-writing brother and sister Bob and Judy to succeed, but he also wants to stage a come-back for their ex-vaudeville step-mother Trixie, who refuses to sing their sort of music. He moves them all to New York, and gets a booking for Trixie at a top night club. Bob and Judy write songs for her under pseudonyms, but when two impresarios want to hire the songwriters to write a show for them, Trixie discovers the truth, and threatens to walk out.