There are two basic types of sound in films - diegetic sound that is part of the story and non-diegetic sound like musical scores imposed on the film. Most films use both diegetic and non-diegetic sound simultaneously. Film sound and music can be used to build anticipation, gradually fade away, provide sudden bursts, create non-melodic tones, undercut dramatic scenes, establish threatening or upbeat moods, and associate motifs with characters to complement and heighten the visuals.