Source Music

People in Real Life usually don't have music following them everywhere they go. But often people do find they've got some underscoring happening in their life—be it from their car radio as they're driving, a band at a bar, or a street musician outside.

Source Music, also known as diegetic music, is Truth in Television in this regard: it's music that the characters can hear, and that would be playing even if the scene were happening in real life. Of course, the music usually serves a dramatic purpose as well: either it helps establish setting and character, or it comments on the action happening in the foreground.

See also Suspiciously Apropos Music and Left the Background Music On. If Source Music becomes Background Music, that's a Diegetic Switch.

Anime

 * An instrumental version of "Let's Stay Together" plays in one episode of Monster, when Roberto and Eva are dancing. In Another Monster, Eva says that this is one of Tenma's favorite songs.
 * Given the realistic nature of the show, all the music in BECK is either played live, on a music player, or played in an Imagine Spot.
 * The music in one scene of the Cowboy Bebop episode "Black Dog Serenade" seems to be diegetic, in that the music stops suddenly when the view cuts to Fad turning off a monitor before going to confront the episode's bad guy.
 * Macross has diegetic music almost everywhere courtesy of there being at least one character who is an Idol Singer. In general, if the song has lyrics, it's probably diegetic, but the score is generally extra-diegetic.
 * Macross 7 was unique in that it had no score, just a guy who really, really, really likes to sing and play the guitar and quite often broadcast it over the entire battlefield. Incidentally, this made all the music of Macross Seven diegetic. Any other instances of music was clearly being played from a radio, such as Sharon Apple's music from Mylene's car radio.
 * Macross Frontier toyed with the line several times, such as during the first episode in which Sheryl is giving a concert at the same time as a battle with the Vajra takes place outside the fleet, cutting between the two locations but never stopping the song, but no one seems to be aware of the other. There's no indication the soldiers could hear Sheryl's song, or that anyone at the concert was aware of the battle taking place..
 * Frontier also gives one of the few cases (possibly the only case in all of Macross) of music with lyrics being used as extra-diegetic: the epilogue of the series has the two lead females talking while the background music is both of them singing the series' main theme song.

Comic Books

 * Lampshaded and played straight in WITCH. The recently arrived at Earth, Orube, comments how funny the TV seems to be here, and the one thing that catches her attention most is that people inside the movies always seem to be accompanied by music in some scenes. At the end of the comic she decides to go out and in that same moment her neighbor is playing the piano, she approves of his playing skills and decides that tune to be her personal soundtrack.

Film

 * The China Syndrome is notable for having only diegetic music. The soundtrack for the movie was disliked and scrapped. In fact, when 1000 copies of Michael Small's original score was released in 2009, it sold out within 24 hours.
 * Laura features multiple scenes at parties and restaurants where live music is playing; all of these are variations on the film's main theme.
 * Matt Monro's "From Russia with Love" is heard over the radio in the film with the same name.
 * And in another James Bond film, the singer in a club sings "Live and Let Die".
 * The 2001 short film My Chorus' revolved around this trope: the main character, Ed, is followed around by a barbershop quartet which provides the diagetic music for his life.
 * Used twice for comic effect in I'm Gonna Git You Sucka. The first time is when John Slade leaves his apartment and is immediately followed down the street by a jazz band waiting outside, playing an instrumental version of the Shaft theme. When he meets up with Jack Spade, who asks who these men are, John remarks that they're "his theme music. Every hero should have some."
 * At the end of the film, a pair of rappers and a DJ with a portable turntable arrived to meet Jack after he becomes the big hero. John Slade asks who they are and Jack repeats the line about theme music. They then perform the music that is used for the ending credits.
 * Almost all music in The Big Lebowski is revealed to be diegetic at some point. The only exception is the stranger's theme song and the music during the on of the dream sequences. The music in the first is shown to be from the Dude's Walkman.
 * Occurs in The Crow when T-Bird pulls up in his car and turns it off, stopping the music as if it had been coming from his car radio.
 * The music in 3-Iron often starts up upon the main characters putting a CD in a sound system and hitting the play button. On one occasion the sound system doesn't start so the lead male decides to fix it.
 * In Oldboy the main character's phone rings with a digitised version of the song "Cries and Whispers" which plays occasionally in a non-diegetic fashion during the film.
 * Almost all the music in Casablanca is played on a piano by the character Sam.
 * Quentin Tarantino is a fan of this trope:
 * Reservoir Dogs: K-Billy's Super Sounds of the Seventies, specifically when
 * Kill Bill: when Elle Driver is walking through the hospital she whistles a tune; there is a Diegetic Switch.
 * Also, with The 5, 6, 7, 8s in the House of Blue Leaves scene.
 * In Part 2, when Budd is in his trailer listening to a record.
 * Death Proof: Jungle Julia calls a radio station to request a song.
 * Any point in Jackie Brown when someone is in their car, a song is likely to be playing on the radio.
 * All of the music in Rear Window is ambient sound heard in the courtyard set, and is a major part of a pivotal moment.
 * The first and second Spider-Man movies both have scenes where street musicians play the theme song from the old Spider-Man television series. The third features the (insufficiently strong) singing voice of Mary Jane Watson.
 * A lot of the music in Rio Bravo is source music, from the playing of Deguello to wear down the besieged to Dean Martin and Ricky Nelson singing and whistling. This was a conscious choice by director Howard Hawks to the overpowering non-diegetic use of the theme tune and song in High Noon. Funnily enough, Dimitri Tiomkin composed the score for both films.
 * Apocalypse Now has the infamous scene in which Wagner's Ride of the Valkyries is played during a helicopter raid as a means of "psychological warfare".
 * In Iron Man 2, Queen's Another One Bites the Dust is played by a DJ at Tony's request when he and Rhodes fight.
 * Then in The Avengers, he overrides the SHIELD jet's PA system to blare entrance music as he swoops in to take on Loki.
 * In Three Kings, when one of the soldiers wants to listen to heavy metal music while going into battle. Another soldier criticizes his musical choice and suggest they go into battle with something soothing to calm their nerves and plays an easy-listening song which also provides a little Lyrical Dissonance..
 * In American Psycho, Patrick plays Hip To Be Square by Huey Lewis and the News while he he murders Paul with an axe.

Literature

 * Invoked by Harry Dresden of The Dresden Files - as he's about to confront a powerful necromancer, he comments that if his life were a movie, dramatic music would start playing, but his life must be really low budget, as all he got was a "radio jingle for some kind of submarine sandwich".

Live Action TV

 * The Bill does this all the time, but it's more pop music than anything plot-specific.
 * Lost has employed various strategies to incorporate source music into island scenes. In the first season, it could only be played on Hurley's CD player, until his batteries ran out. In season two, the Losties found a Dharma station full of vinyl records. As a Musical Gag, the source music was often recorded by artists who died in plane crashes, such as Patsy Cline, Glenn Miller, Otis Redding, and Buddy Holly.
 * Source music on Buffy the Vampire Slayer was often in the form of bands playing at The Bronze.
 * Battlestar Galactica had this in the season finale for season 3, where "All Along The Watchtower" is playing through the Galactica., and in the series finale,.
 * In the season 1 finale of Supernatural, Creedence Clearwater Revival's "Bad Moon Rising" plays in the Impala while The music continues to play afterwards, as we get a view of the   If you listen to the lyrics, they're very ominous.
 * The Wire, as a rule, only uses music that the characters are listening to and no other music, with the exception of one musical montage allowed per season.
 * In the first season finale for Monty Python's Flying Circus, snippets of Percy Faith's "Theme from A Summer Place" was used during the Intermission title cards.
 * Parodied in one episode of Community, which includes diegetic Chirping Crickets during an awkward silence. (Inside the school, during the day.)

Video Games
"Conker: Hey maestro! Don't you think that's a little bit too dramatic? Can you give me something with a bit more of a beat? *music changes* Yeah, that's better!"
 * In the third case of Apollo Justice: Ace Attorney, the hero spends the first phase of the investigation backstage at a rock concert; the BGM is coming from the onstage band.
 * The second case implies that Klavier's theme song really is playing in the court room, as well.
 * In Final Fantasy VI, while one of your characters is impersonating an opera singer, a monster attacks the rest of the party, who end up on the main stage. The Impressario, having had his leading man knocked out by the attack, decides to roll with it, and gets the orchestra to provide the musical accompaniment for the fightscene.
 * Beethoven's "Für Elise" can be heard playing on phonographs in Return To Castle Wolfenstein.
 * The titular mission of Rainbow Six: Eagle Watch has a radio playing rock-n-roll music in one of the offices, and it can be destroyed if it annoys you.
 * Early in Final Fantasy IX, Zidane can hear Garnet singing and looks for her. As he searches, the BGM is Garnet's voice. Subverted in that she's accompanied by a harp in the BGM, but seems to be singing a cappella once Zidane reaches her.
 * Most arrangements of "The Hymn of the Fayth" in Final Fantasy X are ostensibly source music, sung by the Fayth themselves or by unseen monks.
 * In The Legend of Zelda Ocarina of Time, a faint Ominous Pipe Organ can be heard as Link makes his way through Ganondorf's castle, growing louder as he climbs the stairs. Once Link reaches the top, Ganondorf is revealed to be playing the music himself.
 * This trope is invoked earlier in order to navigate the Lost Woods: if the music, which Saria is playing, gets quieter, you know you're going the wrong way.
 * And in the Sacred Grove in Twilight Princess, where the Skull Kid plays the same song on his horn.
 * And lets not forget the man from the water mill in Kakariko Village, who's playing The Song of Storms,
 * Like most Valve games, Portal's soundtrack tends to be very atmospheric and minimalistic, but the first sound in the game is a cheerful samba version of the game's theme song, "Still Alive," coming from a radio in the cell you start the game in. The same music is used later, coming from a very oddly-located second radio, as you navigate a level full of deadly turrets.
 * Alternatively serves as a Theme Music Power-Up for some players, calming them down so they can finish the first "scary" level of Portal. Super effective if they already know the song.
 * Left 4 Dead 2 has jukeboxes and a rock concert scene.
 * When you think about it, all Valve games have Source music.
 * Metal Gear Solid plays Psycho Mantis's theme over some unrelated conversations, and the characters comment on it. It turns out that the tune is actually Mantis's 'mind control music' and a side-effect of using his powers. (Extended canon has that the song is a piece of Russian classical music he remembers from his childhood, and people hear it by 'feedback').
 * The funniest example is in Metal Gear Solid 3, when Snake enters Granin's office, and he's listening to a Sixties pop cover of the Metal Gear Solid theme tune on his record player.
 * Soldier of Fortune II: In the Helicopter Extraction level, the pilot turns on Wagner's "Ride Of The Valkyries" for mood music(the box gets shot out shortly after, though). This, of course is a Shout-Out to Apocalypse Now.
 * Halo: In certain locations, an Easter Egg source music from Bungie's Myth games called "Siege Of Madrigal" can be heard.
 * During the Pvt. Jenkins helmet cam cutscene, the Marines are listening to "flip music"(heavy-metal type stuff) aboard the Pelican. This song is unfortunately not on the soundtrack album.
 * In Halo 3, the song "Under Cover of Night" from the first game is played on a radio in the multiplayer level "High Ground".
 * Outside of cutscenes, the only music in Grand Theft Auto comes from your car's radio - which you can change the station on, or even turn off altogether.
 * In Harvest Moon: A Wonderful Life, the music that plays on your farm comes from a record player inside your house. There are several records you can collect, so you can change said music too, or just turn the record player off.
 * In Ys Book I and II, one floor of Darm Tower features a Twilight Zone-style source music that drains Adol's HP. To stop the evil music, you must break one of the pillars.
 * Fallout 3 has radios (which are oddly still functional after 200 years) sitting around turned on and playing music and other broadcasts from the in-game radio stations. The player also has a wrist-mounted radio that can receive the same stations, with the catch that it is also audible to hostile NPCs and will alert them to your presence.
 * There is also a small amount of nondiegetic background music that is only played at certain times.
 * Conkers Bad Fur Day had Conker getting upset at the music composer during the dinosaur level.


 * In Full Throttle, Todd's trailer has a radio playing awful country music, whose lyrics include "I thank the Lord each day for the apocalypse".
 * In the very beginning of Xenogears, Fei and Citan listen to music from a device Citan found. It serves as the Nostalgic Music Box theme.
 * In The Conduit, there is an elevator in an enemy base with very suitable elevator music coming out the speakers.
 * The Nightclub music in Perfect Dark Zero, which grinds to a halt when you pull the fire alarm.
 * There's one boss fight in Master of the Wind set to "Spirit Never Dies" by Masterplan. This is because the fight takes place in the middle of a rock concert. With the lead singer and his band of summoned music angels. It's in the running for Best Boss Ever.
 * The main protagonist of Persona 3 is never, ever seen without his Atlus Audio MP3 player. He was even listening to the game's opening theme, "Burn My Dread," as he headed for the train station that would take him to his new home in Tatsumi Port Island. He listened to it on the train, for that matter, and during the —it must be his favorite.
 * The final mission of Soldier of Fortune: Payback is set in a dance club, with a diegetic techno soundtrack.
 * Fairly common in the Fatal Fury series. In Fatal Fury 2 and Special, Krauser has a 90-piece orchestra in the background of his stage, obviously supplying the orchestral music. In Fatal Fury 3, the background music in Terry's stage only starts when a character turns on a radio. In Real Bout Special and 2, there is an opera singer visible in Krauser's stage, and she sings in time with the vocals of his new theme.
 * Aquaria is an interesting case: the BGM heard throughout the game.
 * Ace Combat 5 The Unsung War has music actually playing in-universe at two points. The first is when the squad is celebrating their destruction of the Hrimfaxi submarine - interestingly enough, the music is taken from the game's arcade mode. The second is at the start of the "Sea of Chaos" mission, where Captain Andersen plays "The Journey Home" over the Kestrel's loudspeaker, though after about a minute it undergoes a Diegetic Switch.
 * Unusually for a fighting game, the music in most Power Instinct games is diagetic - you can see the musicians in the background performing the song in each stage.

Web Original

 * In the first episode of RWBY (V1E1), Ruby Rose is listening to what turns out to be the first volume's theme song on a set of headphones when she is threatened by a robber in a shop she is in. The music is faint and tinny -- until she springs into action and ends up in the street with an unfolded and massive Crescent Rose, at which point the music is clear and crisp.  And then she turns it off.

Western Animation
"Fry: Yahoo! Crank up the stereo! (Fry turns on stereo) Stereo: "We're whaling on the moon-" (Fry turns off stereo hastily)"
 * If you pay close attention, the only time there's nondiegetic music in Metalocalypse is during a Montage.
 * True, but that show uses montages with great frequency anyways.
 * Despite being billed as a "musical fairy tale," only one of the songs in Barbie and the Diamond Castle can be considered non-diegetic: the villain's song, "Wonderful Me." And even that may be diegetic, as her minion applauds at the end.
 * Happens often in Futurama. One example is when Fry goes to the moon. He ventures out to the real moon, and prepares to crank up the radio. Unfortunately the only track playing is 'Whaling On The Moon'.


 * Happens at the end of one episode of Squidbillies, where the usual credits music is playing in-universe. After about two seconds it switches as the credits actually come up... and then two more seconds later, the credits and the music disappear entirely, as Granny comments "nobody cares who these people are!"