Diegetic sound, and by extension non-diegetic sound, is a fundamental concept of sound design that can get more nebulous the more you explore the craft. While the distinctions between the two are somewhat obvious once you are familiar with them, the difference between them can become blurry within the context of genre and more impressionistic styles of filmmaking.
In this article, we hope to dispel any confusion around the terms, explore the questions they raise, and highlight some examples of how diegesis has been handled in film sound to create interesting results.
Diegetic sound refers to sonic elements that occur within the storyworld of the film, meaning any sound that is actually caused by or happening externally to the characters. This includes everything from onscreen dialogue and footsteps to offscreen ambiences such as birdsong and traffic.
Due to films usually telling stories that exist within a shared reality, by default, most dialogue, Foley, and sound design happen within a film's world. If a character is hearing it, more often than not, you would describe the sounds as diegetic.
Non-diegetic, or sometimes known as non-literal sound, can be described as any sound happening outside of the reality of a film. This can be as fundamental as voiceover narration or the score; if the characters can’t hear it, then it is non-diegetic sound.
Non-diegetic sound can also be used to describe sound effects that portray the subjective internal world of a character, representing emotions and mental states. This kind of non-diegetic sound is more impressionistic and may contain elements of diegetic sound processed with extra audio effects, or be entirely textural, supplementing the score to convey what emotions should be felt.
Diegetic music is part of diegetic sound. For it to be diegetic, it must occur within the reality that the characters inhabit. Maybe there's a scene that features a live performance, or radio playing through a loudspeaker, or a character listening to music in their headphones… these are all examples of diegetic music. On the other had, if there's just a 'theme song' playing, and the characters can't hear it, it's non-diegetic (more on this below).
When mixing diegetic music, care should be taken to add sonic characteristics that inform the ear that it is emanating within a space or from a medium: reverbs, speaker emulators, realistic panning, etc. It shouldn’t sound like a studio multitrack recording has just been placed within the edit timeline. Otherwise, the viewer might not be able to ascertain where the music is supposed to be coming from.
That being said, musicals often forgo these steps as the storyworld of the film already exists in a heightened reality.
As previously mentioned, the score and narration are usually considered to be non-diegetic unless explicitly shown to be otherwise, such as the narration being a radio show or the score being performed by an in-universe band. Although the argument could be made that they remain non-diegetic until revealed to be otherwise, or vice versa. Internal monologue is not usually considered to be non-diegetic.
Non-literal SFX can also blur the line between non-diegetic music and sound design, as sonic storytelling techniques such as soundscapes, hits, or stings can overlap between the two. In some films, it may be hard to tell what sounds are coming from the score or the sound design. This can create an interesting relationship, where similar sound palettes can be used by both in different ways, allowing for a cohesive overall sonic identity for the film and an interplay between the two. This is more common in genre films such as horror or sci-fi.
A helpful way of bridging the gap between diegetic and non-diegetic sound is with Trans-Diegetic Sound. This can literally be the combination of diegetic and non-diegetic elements, or a literal transition from non-diegetic to diegetic. Such as the score starting as a needle drop but moving into the ‘real world’ by transitioning to the song playing from a radio.
That being said Trans-Diegetic doesn’t solve all our previous questions. When does it stop being non-diegetic and start being trans-diegetic? Aren’t most film soundtracks trans-diegetic, as they usually have real-world dialogue alongside the score?
We have selected a few interviews and scenes from films that help illustrate the difference between Diegetic and Non-Diegetic, and how playing with diegesis can lead to interesting results.
Foley is often a great example of diegetic sound; it directly places the characters within the world and helps the ears focus on what’s important. In this case, some fantastic Foley work that aids in telling the story, using the rattle of cutlery and groans of the floorboards to convey the sheer weight and strength of the character.
Non-diegetic sound can help set the tone of a scene, enhancing its overall cinematic qualities. In this example, the line between score and sound design is blurred. The score uses sounds reminiscent of the sci-fi engines or the world, and the sound design uses folk instruments. Coming together to aurally portray the atmosphere of this overwhelming cityscape.
In this classic sequence, the lines between score and sound design are blurred even further as we’re put into a similar meditative state as the characters. Starting with a sparse score and the diegetic sound of the railcar. They slowly combine through complementary rhythmic additions to the score and post-processing of the diegetic sound. Moving to and from the real world and creating a dreamlike monotony.
The free-flowing energy of Birdman greatly benefits from its jazz drum score by how it complements the in-the-moment feel of the cinematography. But with a narrative as meta as Birdman’s, moments where non-diegetic music becomes diegetic enhance this cohesion further. In this case, the score moves into the filmworld in the sound mix, gradually placing it within the streets of New York until the ‘real’ drummer is revealed.
2014 was a great year for jazz drumming in cinema. In Whiplash, at the climax of the story, we are treated to a drum solo that manages to conclude the psychological warfare of the narrative. All the tension is finally released, and the sound mirrors that. As we focus on Neiman’s double time swing, the diegetic sound is gradually pulled away and replaced with a hushed wash of noise. We are in Neiman’s flow state, an earned moment of stillness amongst the cacophony.
Most sound in film is unrealistic, an exaggeration of how things sound in the real world. Even if it is done in a naturalistic style, SFX such as fire will sound extra loud, or Foley elements will be more overt than they would in reality. Explosions and silencers on guns, for example, usually sound very unrealistic because we have learned to expect certain sounds to represent them in film.
Sound design is an art form; whatever works for the story works. These terms are descriptive and not guidelines. Most film sound consists of diegetic and non-diegetic elements happening simultaneously, and the interplay between the two can result in new and interesting ways of telling a story. Where these terms become hard to define is usually when a film is doing something interesting that can be interpreted in many different ways, so don’t get too bogged down by it. Leave that to the academics.
Instead, it can be helpful to think about diegetic and non-diegetic sound in broad strokes, moments where you want to move away from the real world and come back to it. Do you want to go inside a character's head or perhaps distance them from the audience? Strip all the sound away until you are left with just the score, or bring the audience crashing back to reality? It’s moments like these where playing around with diegesis becomes an invaluable tool in any sound designer's arsenal.