Fox Movietone Follies of 1929 (1929)

Lila Beaumont is an understudy in a Broadway musical. Her boyfriend, George Shelby, arrives in New York hoping to take Lila back home with him to marry. George buys a majority interest in the show, planning to fire Lila after she refuses to quit the show. But when Lila goes on in place of the temperamental star, she is a great success and George is able to sell the show back to the original investors at a profit.