Non-Diegetic Sound

Non-diegetic sound is sound that comes from outside the film. This means the characters cannot hear it. The most common forms of non-diegetic sound include sound effects, narration and incidental music.

Non-diegetic sound is fundamental to a film in the way it allows an audience to connect with the characters and to also feel involved in the movie. It also causes us to develop strong emotions for what is happening. For example, in a horror movie the use of incidental music and harsh, loud sounds causes us to feel scared. Particularly in these scenes, incidental music heightens emotions. In Marley & Me non-diegetic dismal music is played in the background which makes us identify with the main character further so we too, feel as dolorous as him.

Without non-diegetic sound effects and music, an action scene ultimately can't be powerful. If you were to take out the music for an action scene it instantly reduces the effectiveness of the choreography and stunts and makes the film dramatically bad. But add fast-paced, loud music to match the intensity of a fight scene and you have a respective fight scene that will leave audiences awe-struck for days. If you look at The Amazing Spider-Man 2 erratic music, a sound motif and violent, striking sound effects make the fight with Electro much more exciting, compelling and dramatic.