Diegetic sound is any sound that originates from the world of a film, meaning that if the characters can hear it, its diegetic. Diegetic sound can be on-screen or off-screen, and it includes dialogue, sound effects, and music that occurs in the story world. Non-diegetic sound, on the other hand, is added in post-production and is not heard by the characters in the film. Examples of non-diegetic sound include musical scores, narration, and custom sound effects. The highest quality films use a mixture of both diegetic and non-diegetic sounds to drive storytelling. Diegetic sound adds realism to the content and helps viewers suspend their disbelief, while non-diegetic sound can be used to create a specific mood or emotion.