He's My Guy (1943)

Vaudeville performers Van Moore and Terry Allen split up after a quarrel. Terry moves in with Madge Donovan, a dancing comedienne friend. She gets a job as secretary to Kirk, personnel manager of a defense plant, and conceives the idea of staging a talent show from among the workers. She sends for Van to help her stage the show but he arrives and finds her with Kirk and they break up again. When the show goes on, Kirk takes bows for its success. When it comes Terry's turn to sing, she is terrified without Van. But when she hears her accompaniment, she knows it is Van playing it, and walks out on the stage to find him at the piano. Madge tells the plant president that Van, not Kirk, really produced the show and he announces that Van and Terry are now co-directors of the entertainment for all the company's plants.