Sound in media is typically split into two forms: Diegetic and Non-Diegetic. Diegetic is roughly equivalent to In-Universe — the characters can hear this sound. Non-Diegetic sound is "audience-facing" — only the audience hears it, but it is still a significant part of the story.
Not all Dialogue and Music Tropes directly relate to diegesis, as individual sounds can, in different situations, be either non/diegetic or both. Listed below are tropes for which diegetic status is integrally important to meaning.
When a work creator makes use of a sound restriction or lack thereof, it has various creative purposes. There are different levels of characterisation, of story development, and of juxtapositional relationships that can be influenced by where sound originates and where it goes. And sometimes, it's just for humour.
This is an Omnipresent Trope, which means that you could say "Work X uses Audio Diegesis in this way for this purpose", but you should use the more appropriate trope below.
Tropes dealing with diegetic sound:
- AM/FM Characterization: The music a character likes is used to demonstrate their personality.
- Acoustic License: White noise being dimmed down to make main characters' speech/important sounds more easily audible.
- Diegetic Musical: Some or all the performances in this musical are occurring "in real time".
- Interscene Diegetic: A piece of music within the work flows from one scene to another.
- Source Music: A work where in-universe naturally-occurring music forms a "real-life" soundtrack for characters.
- Suspiciously Apropos Music: Lyrics of songs played within a work relate to the plot, often used as foreshadowing.
Tropes dealing with non-diegetic sound:
- Audible Gleam: An object's lustre sounds like a wind chime.
- Background Music: The pieces of music underscoring a work, for the benefit of the audience.
- Establishing Character Music: A backing track to a character's introduction that aligns with their personality.
- Kung-Foley: Serious action sequences using hyper-exaggerated sound effects.
- Laugh Track: A standard snippet overlaid on sitcoms in post-production to (subconsciously) tell the audience when to laugh. On occasion it can be played for humour as being diegetic in a cut-away gag.
- Leitmotif: Recurring musical accompaniment associated with a certain character, setting or action.
- Musical Spoiler: A change in background music is an early indication that something is about to happen.
- Reality Has No Soundtrack: A work without a soundtrack, often promoting realism.
- Scare Chord: High-pitched chord used to reinforce a Jump Scare.
- Silent Credits: Credits sequences with no sound.
- Sound-Effect Bleep: Censoring diegetic sounds, usually dialogue that's considered unsavoury, with an audible tone. Can be played as diegetic for humour.
- Sting: A sharp musical sound effect.
There are also times when the diegetic barrier is crossed, there are tropes that deal with this:
- Diegetic Soundtrack Usage: When a work's soundtrack (in instances when the theme was created for the work) appears within the universe of the work.
- Diegetic Switch: A piece of music plays within the work and then transitions to the soundtrack.
- Flashback... Back... Back...: When diegetic sound is echoed into non-diegesis to represent a flashback.
- In-Universe Soundtrack: All or many of the soundtrack pieces (i.e. background music) are also being played from within the work.
- Left the Background Music On: Some sounds that appear to be non-diegetic (sound effects, background music) are afterwards revealed to be played within the work, Breaking the Fourth Wall.
- Mickey Mousing: The action on screen is represented by sound effects. In cartoons, the character's actions are often making the sounds.
- Music Video Syndrome: A music video using cinematography and editing to match the beat of the visual with the beat of the audio.
- Musical Gameplay: Games where the background music is immediately affected by what happens on the screen.
- Musical World Hypotheses: Varying levels of diegetic continuity regarding songs within Musical works.
- Opening Narration: When a character from within a work delivers a speech or form of exposition to the audience.
- Plot-Based Voice Cancellation: A loud in-universe sound covering up an important line of dialogue so that both the characters and audience cannot hear it.
- Jackhammered Conversation: An in-universe recurring noise keeps the audience (and often some of the characters) from hearing several parts of a conversation.
- Transition Track: A piece of music introduced at the end of a scene deliberately to bleed into the next, not existing within the work during the previous scene and edit.
- Virtual Soundtrack: When a written work, often fanfic, has a character listen to or describe music in a way that suggests the reader do the same, to create a soundtrack effect for the story.
- Written Sound Effect: Sounds produced by in-universe actions, in written media, being represented by onomatopoeia for the reader.