Deep in My Heart is the MGM-ified biography of composer Sigmund Romberg, here played by José Ferrer. Evidently the scripters didn't feel that the life of Romberg (as set down by author Elliott Arnold, whose book was used as the film's basis) had enough drama to fill out two hours and ten minutes. As a result, the film is overstocked with guest stars, performing such Romberg standards as "One Alone," "Lover Come Back to Me," "When I Grow Too Old to Dream," "Will You Remember," and "Stout-Hearted Men." Among these celebrities are Ann Miller, Vic Damone, Jane Powell, Tony Martin, Cyd Charisse, Rosemary Clooney, and Gene Kelly, the latter performing a dance duet with his seldom-seen brother, Fred. For all the heady competition, it is José Ferrer who renders the most memorable production number: a one-man presentation of the Romberg musical comedy Jazzboat, in which Ferrer assumes all the roles, from star Al Jolson's to the entire female chorus!