Clearly defined melodies that are "developed" (or altered and commented on) in a composition; for short musical themes, the terms 'theme' and 'motive' are essentially interchangeable. In film, a musical theme functions like the literary motif, a significant recurring sound element. [See also leitmotif and motif] Buhler, James and David Neumeyer. Hearing the Movies: Music and Sound in Film History. Oxford UP, 2015.