Originating from the Greek word for narration, diegesis is used by filmmakers to denote ‘the world of the film’. In essence, that means everything that exists within the story or narrative is diegetic. With that in mind, when musicians and producers talk about diegetic music, they are referring to any sound that emanates from a source within the film’s reality. Alternatively called ‘source music’, this type of sound can come from things like a radio, stereo, or live musicians placed within the film. At times, it may be that the audience are unable to see where the music is being played, but as long as they know that the characters are hearing the same melody that they are, it is diegetic.
Quentin Tarantino is renowned for his use of diegetic music. In Pulp Fiction, the film begins with ‘Jungle Boogie’ by Kool and the Gang. As the film transitions into the opening scene, we discover that the song is actually being played on Jules and Vincent’s car radio. In the same film, Vincent and Mia dance to Chuck Berry’s ‘You Can Never Tell’, during the iconic twist contest scene at Jack Rabbit Slims; another example of diegetic music.
Diegetic music is any music that comes from within the film, then it makes sense for non-diegetic music to be any music that exists outside of the film or any music that the characters are unable to hear. In comparison to diegetic music, this form tends to be a lot more common in films. It may be that instead of non-diegetic music, you have heard interchangeable terms such as ‘underscore’, ‘interpolated music’, ‘commentary music’ or, most probably, ‘background music. All these terms ultimately mean the same thing and aim to reflect how the character is feeling or their psychological state. Equally as important, non-diegetic music helps the audience understand how they should be reacting to what they are seeing.
These scores are used to help the audience fully immerse themselves in the film and the fictional world that they are presented with. This makes them especially vital in fantasy films, where the audience are asked to suspend their disbelief for a few hours, if not more. If the music does not enhance the imaginary narrative that the audience follows, it will lose any appeal. Undoubtedly, some of the most obvious examples of non-diegetic music being used successfully are Star Wars and Lord of the Rings. Each battle is emphasized with dramatic scores and each love story is told through romantic melodies.
In some films, it is difficult to fit the music into the binary categories of diegetic or non-diegetic. Instead, Earle Hagen argues in his book, Scoring for Films, that a third category exists where both combine: source scoring. Despite some arguing that there needs to be a delineation between diegetic and non-diegetic music, source scoring allows the score to perform both functions without any major changes to the musical content. For some, it can be challenging to differentiate between source music – or diegetic music – and source scoring. In the words of Hagen, “source scoring takes on a much closer relationship to the film. It follows the framework of the scene more critically and matches the nuances of the scene musically.”
A relatively contemporary example of source scoring is American Graffiti. The music for the film consists of popular songs from the 1950s and 60s. At face value, the majority of these songs emanate from the car radio, making them diegetic. However, under deeper analysis, the way in which the music and the song titles link with the scenes and what is said within those scenes, suggests that there is something more nuanced at play. For instance, when Carol first gets into John’s car, Buddy Holley’s ‘That’ll Be the Day is playing on the radio. Arguably, this is an ironic commentary on the possibility of a romance between the two. However, when John embarrasses Carol by suggesting he is babysitting her, we hear The Monotones ‘Book of Love being played as he goes to chase after her, which suggests his feelings may have changed and foreshadows a possible romance between the two.