To a generation of moviegoers who may not have had access to Broadway musicals in New York or on tour, the barrel-chested Mr. Keel was what a musical comedy leading man looked and sounded like: Tall, handsome, with a voice that could be muscular (as in M-G-M's "Kiss Me, Kate," in which he played the swaggering stage actor Fred Graham) or tender and longing (in M-G-M's "Show Boat," singing "Make Believe" as a river boat gambler wooing a virginal girl whose parents run the title Mississippi venue).