The Detective Conan anime is very structured musically. For example, if you hear a little "DUM!" or a similar sound, chances are Conan was looking at a very important clue. Further more, every specific moment of each episode has a fitting theme so if you hear the happy sax song, bad guy's screwed... And if you hear sad sax song, bad guy will say how unfair life was to him.
In Sailor Moon, the title character's attacks had their own background music. Occasionally she started her attack but the 'tense' or 'battle' music would continue, which was a sure sign the attack would fail (either because it was So Last Season or to show the enemy she was facing was not just any random monster of the day.)
In the Ghost in the Shell: Stand Alone Complex episode "Trial", the instrumental intro of I Can't be Cool is played over a speech by Togusa. I Can't be Cool is usually played when The Major is hacking. Later in the episode it's revealed that she hacked Togusa's brain to deliver that speech.
Fullmetal Alchemist contains a subtle one. Near the end of the series, when Lyra is leading Rose to a church, Dante's motif begins to play. This is because Dante has already taken over Lyra's body. This is revealed in the dialog not too long afterward, but this hint helps piece it together earlier.
Dante's leitmotif is a spoiler by itself, since it has a very Obviously Evil feel to it, but plays before she's revealed to be a villain.
In the Digimon series, if a digievolution is running but there's no music at all (or, sometimes, the regular fight or ambient track that was playing before), you can be sure the transformation will not be finished or turn to be a dark form instead of the regular one. Played more straight in the Adventure and Adventure 02, when there are fewer soundtrack options than the sequels.
Inverted in the trailer for Naruto Shippuden Episode 248- the normal musical lead-in for the trailer is replaced by screams of terror, as we finally get to see the Nine-Tailed Fox attack.
In the first episode of Kill la Kill, when Ryuko is first revealed to be wearing her Kamui Senketsu "Blumenkranz" starts playing. The fact that this is the theme music for Ragyo Kiryuin Ryuko's mother, not that Ryuko knows at the time is not at all a coincidence.
In Clear Skies 3, the Scottish funeral dirge "Flowers of the Forest" begins playing when the Magellan launches an attack against the enemy fleet. Sure enough, the ship does not survive.
Done straight and subverted in Jaws. Every time the real shark appears, its classic theme plays; notably, it doesn't when the fake shark appears. Subverted in the second half of the movie, which plays the theme a few times as a red herring, and withholds the theme before the shark first encounters the Orca.
In Twelve Monkeys, the "12 Monkeys" leitmotif (a bandoneon song played by Astor Piazolla) plays during one of Brad Pitt's rants; this is the first clue that he's a member of The 12 Monkeys.
In Cabin Fever, an extremely sinister soundtrack is played during a sex scene. As the soundtrack indicates, there's a grim side to this encounter: the healthy-looking woman was passing the disease to her lover. At the same time, her lover was passionately squeezing her back, which bought sickly red rashes out on her skin - revealing to the audience that the woman was already infected with the titular disease.
Not much of a spoiler, but if you know the leitmotifs in The Lord of the Rings, you can immediately tell that the charge on the Warg-scouts on the first part of The Hobbit is by Elves. Though the fact that it's a militaristic version of the Lothlórien theme playing rather than the Rivendell one might throw you off.
The soundtrack album for The Phantom Menace was released two weeks before the film's premiere. It listed all the musical pieces in the upcoming film, which were titled based on the scene they appeared in. Among these titles listed were "Anakin Defeats Sebulba", "The Death of Maul", and "Qui-Gon's Funeral".
In Law & Order, whenever music starts, you know something extremely plot-relevant is about to happen. To figure out what, just check the clock. Less than 20 minutes in? The plot thickens. Less than 3 minutes left? It's time for the Motive Rant.
The series also has a piece of music that is almost exclusively used when someone important to the case has committed suicide (or been murdered).
In the Game of Thrones episode "The Rains of Castamere", the fact that the titular song (written in honor of the Lannisters crushing a rebellious House) is being played during Edmure Tully's wedding is the first sign that something is horribly wrong.
In the Doctor Who episode "Army of Ghosts", as soon as the Cybermen tell the Doctor that the Void Sphere doesn't belong to them, the Daleks' theme music starts playing. Guess what comes out of the Sphere about a minute later.
If you listen to the Series 6 soundtrack before you watch the show, you might want to skip "Tick Tock (Vocal Track)":
Tick tock goes the clock
'Til River kills The Doctor.
Done all the time in the Dutch detective show Baantjer, to the extent that you can pay attention only when the "suspect is saying something important" music is playing and still get all the details on whodunit.
In Firefly, You could always tell when the Reavers were going to show up by the bass-heavy, metallic-sounding music that played along with their arrival. Best heard at around 2:35 here.
The Collector Ship Theme in Mass Effect 2 borrows heavily from the Reavers' music, and like there, it starts playing just before OH GOD WHERE'D THAT GIANT SHIP COME FROM?
Lampshaded on Mystery Science Theater 3000 in the episode The Hellcats. Crow is wondering if the main character can back out of a challenge he's just been faced with, and Tom replies, "No, it's too late, the music already started."
On Who's Still Standing?, every time the music starts to get louder, there's a commercial break coming in about 15 seconds, unless the show recent returned from commercial, in which case someone's going out on the current question.
NBC game shows in general have a nasty habit of using musical stings to telegraph the action; whether it's the question deliberation music on 1vs100 ramp up when a contestant is about to lock in an answer, or Identity's music ending just as an answer reveal is about to take place, savvy viewers will be able to know what's going to happen just by paying attention to the music beds.
In the series 4 finale of Skins, the music cuts in just before Naomi's finished her Anguished Declaration of Love cum apology to Emily; the tone of the music makes it pretty clear how Emily's going to react.
In a case of soundtrack titles acting as spoilers, the leaking of the track titles for the final season of Spartacus: Blood and Sand caused a minor meltdown in the fandom when two of the tracks were revealed to be "Gannicus Crucified" and "Agron Crucified" (although the latter also has a track called "Agron Rescued").
CSI: Crime Scene Investigation: A seemingly normal family (mom, dad, teenage son and daughter) has disappeared, leaving an empty house and an unknown woman's body. The investigation reveals that the unknown woman had an affair with the dad in order to extort money from him and was confronted by the family and wound up being killed by the mom mid-smug monologue ("I just wanted her to shut up!"). One family member is found alive, claiming they slipped out while the others went to a movie and during the evidence processing montage this song is playing, which sounds a lot like something a teenage girl would listen to and it turns out that one's a killer: she murdered her brother because he killed their father for having the affair that started all this and killed her mother because she killed the other woman and forced them to go on the run. Their motive rant boiled down to "everyone kept making rash decisions without thinking of the consequences (especially towards me) and I couldn't take it anymore".
Parodied in this Onion piece, where ominous music starts playing across the USA, sending the media into high alert.
Stand Up Comedy
Eddie Izzard refers to this in one of his routines about horror movies.
"They never listen to the music, do they?"
In the tabletop RPG In Nomine, followers of Nybbas, the Demon Prince of Mass Media, can gain the supernatural ability to hear background music. Changes in the background music can warn them of danger.
The power for a PC to hear the background music also appears in Tales From The Floating Vagabond as one possible effect of the "Rogers and Hammerstein Effect" shtick.
If the music in Halo makes you think "How did they MAKE those sounds?!" then load your shot gun and bare your Energy Sword, you're about to be Flooded.
In Chrono Trigger, you know when Lucca, Frog, Robo, or Ayla is about to do something cool because their Leitmotif starts playing.
In Chrono Cross, after the incident at Opassa Beach where you first travel between the dimensions, the first clue that you're not in your own world anymore is that the overworld music has changed from "Fields of Time" to "Dream of the Shore Near Another World".
In Ace Attorney, if you make a correct "Objection!", the music stops. If the music continues, you know you messed up even before the judge yells at you and takes away part of your Life Meter.
Also played for laughs. Near the end of one case (1-3), Edgeworth senses the witness on the stand is the guilty party, prompting him to take the first steps toward his Heel-Face Turn. He shouts, "OBJECTION!" and the epic music starts playing. The Judge questions him on his objection, and the epic music dies, as Edgey responds he didn't have a reason. After a beat, OBJECTION! *cue epic music* Edgeworth has something now.
Also subverted for the Grand Finale in Trials & Tribulations. Even if you pick the right selection to implicate Godot, the music continues, to trick you. Godot's initial response is the same for success or failure; either way, he'll respond by accusing Phoenix of not being half the lawyer that Mia was...but, if you picked the right choice, the music will stop after that so Mia's ghost can appear to guilt-trip Godot so Wright can make his point. If you pick the wrong choice, Phoenix starts stammering like an idiot and you get a Guilty verdict.
In Ace Attorney Investigations, when Confrontation: Presto plays, you know whoever you're cross-examining is the killer. The second game subverts this. It still signifies a Wham Episode, but that doesn't necessarily mean you're cross-examining the killer.
Actually, the first Investigations game contains a subversion as well: Confrontation Presto plays when Edgeworth is cross-examining Shih-na a.k.a. Calisto Yew in disguise, but Shih-na/Calisto Yew isn't the killer, she's just an accomplice and is instead guilty of arson, and the real killer is Quercus Alba, who's cross-examined later on.
It doesn't happen for the boss in the Long Library, though.
In Final Fantasy IX, the intro to the "Fairy Battle" theme is meant to sound just like the intro for a standard battle, probably to avoid the Musical Spoiler — but the instruments are different enough that if you're paying even a bit of attention, you can tell the difference.
It's fairly obvious that Seymor is a villain in Final Fantasy X. If you don't get it by his looks you will surely get by his creepy leitmotif.
Not avoided at all in Final Fantasy VII if you have the Chocobo Lure materia on. You will know right away whether there's a chocobo in the encounter or not, even while the battle transition is still happening.
In XIII-2, a slightly different victory theme plays if you achieved a 5-star ranking on a battle. Since the victory music starts up the moment the lat enemy has been killed, you know how well you did long before getting to see your actual rank.
Akitoshi Kawazu has a lot of fun playing with this trope in his work for Square:
In SaGa 2 (Final Fantasy Legend II in the U.S.), the heroes are spying on a secret meeting between several villains. As soon as the villains spill the beans on their nefarious underworld dealings and the Heroic Tune fires up. The villains all start looking around, asking "Where's that music coming from?!", then you bust in on them.
In Final Fantasy Crystal Chronicles: Echoes of Time, the party reaches the end of a library-themed dungeon and runs into a spacious arena-style gallery as the boss fight music strikes up, then peters out as the heroes look around and no boss monster is evident. Then one of the bookcases grows teeth and claws, and the boss battle music kicks in for real as it attacks.
In Dragon Quest IV, Chapter 3, Taloon will sometimes run into traveling merchants. Since these traveling merchants are accompanied by the town theme instead of the standard battle theme, you can tell you're OK as soon as the music starts.
In Dragon Quest VIII, if you successfully flee from a battle, your first indication is that the music stops.
Lampshaded in Final Fantasy Mystic Quest. Every time Tristam is about to make an appearance, his Leitmotif plays, and the main character reacts in surprise and starts looking around for him.
At one point in Metal Gear Solid, your comrades actually advise you to listen to the volume of the background music in order to judge whether a helicopter is near you or not.
Plus Snake actually wonders aloud "What happened to the music?" shortly before the battle against Psycho Mantis.
Given that Psycho Mantis' entire schtick is that he has No Fourth Wall (you beat him by switching which port the controller's plugged into) this is unsurprising.
In Metal Gear Solid 2Olga's theme plays whenever she is in the scene and only when she is in the scene, from her very first appearance. This particular theme of hers plays when Raiden is about to be shot by Revolver Ocelot and then the ninja shows up to save him, nearly cutting off Ocelot's hand ala Metal Gear Solid and at the end when the ninja jumps in to knock Taiden out on Snake's command, revealing it to be Olga decked out as the ninja. Anyone who listened to the game`s OST will recognize the theme.
And then, as the voice actor credits roll at the end of MGS4 you may be wondering "Why is Big Boss's Leitmotif playing?", then, "Why does Big Boss have a voice actor credit?", and then, "How can Big Boss possibly still be alive?!"
In Banjo-Tooie, an ominous theme (aptly named "There Comes Trouble...") always starts playing when the duo is about to face a Boss Battle. Eventually, upon entering a curiously empty room, Kazooie points this out by declaring: "The music's changed. Every time that happens we always end up in a fight," before, oddly enough, fighting Klungo for the third time.
Subverted in the same game, in Terrydactyland. Considering the number of massive dinosaurs about, it helps add to the grandeur of the area, but it's still bizarre. An area obstacle (to be fair, an irritatingly difficult one) gets the ominous theme and boss description (Triassic Steamroller). A minigame gets the ominous theme and boss description (Stomach-Cramped Carnivore). A completely harmless NPC gets the ominous th... no, no theme, but he still gets a description (Seeker of Beverages). Even the actual boss of the area becomes a friendly NPC after his defeat.
Egregious in Deus Ex, where the music is the best way of knowing if you are detected by the enemy.
Also Splinter Cell, the best way to know if you've been seen is if the music suddenly starts. Being a stealth game, the music is usually off. Also - not sure if you've killed everyone after being seen? Listen to the music. Especially in the first game, it'll start winding down the moment you're in the clear.
In Painkiller, you know when enemies are about to attack because the heavy metal soundtrack will kick on, and you know you've defeated all the enemies in the current area when the music fades away.
The 3D The Legend of Zelda games all replace the normal music with a combat theme when an enemy is near. In addition, The Legend of Zelda: Twilight Princess also had a special remix of the Hyrule Field overworld theme that plays whenever you've exposed an enemy weakpoint, and is generally your cue to commence button mashing (or Wiimote waggling) to get in as many sword-hits as possible before the boss recovers.
In addition, in The Legend of Zelda: Phantom Hourglass, the easy way to tell if you're being chased by the Phantoms in Temple of the Ocean King (other than the giant "I HAVE YOU NOW" or whatever across the bottom of the screen) is by listening to the music changes. When the ominous music goes away, you know they've stopped chasing you.
Boss battle themes don't usually spoil since they only start after the enemy has been "introduced" to you. However, the music stops when you first enter a boss room, and the series isn't known to throw you into unexpected boss battles. Also, the boss music itself usually stops once you've landed the final hit on the boss, signifying that you've beaten it (though the fact that the game also switches to a cutscene of the boss dying can be a spoiler before even that).
Even the very first The Legend of Zelda, which didn't use boss music, warned you when you were approaching boss territory. If any of the adjacent rooms held the Dungeons boss there would be "roaring" sounds every few seconds. Though some boss like monsters would make those sounds while onscreen anyway.
In The Legend of Zelda: Skyward Sword, the melody of the Goddess' Song, the game's main theme, is Zelda's Lullaby played backwards, foreshadowing the fact that Zelda is the Goddess.
There's a severe difference in style between the normal background music and the fight music in Devil May Cry. Thus, if you enter an area and the music abruptly shifts gears, get your sword out. This is especially true for the third game, where the fight music has vocals.
Occasionally, when you kill an enemy in God Hand, their soul becomes a demon and attacks you. You'll know it when it happens, even if the enemy is offscreen, because the music suddenly switches to a distinctive guitar sequence (or, if one of the horribly powerful Four-Armed Demons arrives, an orchestra).
In Tales of Symphonia, if it wasn't obvious that the thing you went to the Latheon Gorge to get has a boss guarding it by genre alone, the music stops when the enter the room.
In Cave Story, it is immediately obvious when the fight with Perfect Run Final Boss Ballos begins that the form you start out fighting won't be the only form, as the music then playing is the miniboss or minor boss theme.
Even before that, you can be certain that the Doctor isn't the final boss because of the music.
An earlier boss battle subverts it. The player activates a robot which attempts to destroy him, and in the robot's dialogue the standard boss music starts playing. Then the music is suddenly cut off as Balrog steps on the robot.
The Sonic Advance Trilogy has the "Boss Pinch". When a boss hits critical HP, the music suddenly changes to reflect it. The first games featured a total different tune for the Boss Pinch but in the third game, it's actually an awesomely frantic remix of the regular boss theme.
The same thing happens in Bomberman Generation. The music switches to a variation of the Standard (Multiplayer) Battle theme when a boss is in critical condition.
Sonic Generations, if you know your Sonic music. While standing outside a stage / boss, a medley will play. If you can correctly guess where the medley comes from, then you have an idea of what to expect.
Averted for the last two bosses. The sixth boss plays a remix of E.G.G.M.A.N. from Sonic Adventure 2 it's actually the Egg Dragoon from Sonic Unleashed, and the final boss plays no music at all.
Ah, but remember: at that point of the game - the first time through, of course) - Revan's theme hasn't played yet (well, not in actual relation to Revan).
Parasite Eve does this fairly often; when a boss is in the next room or a major event has happened, the music will stop. Also occurs during the Bonus Dungeon when you arrive in a very large room where a boss would be.
Hostile NPCs (and animals) in Gothic tend to chase the player if he tries to flee from a fight. It's possible to tell when they've given up the chase without having to turn and look, because the dramatic music stops playing.
You can tell how close you are to winning or losing a boss fight (on foot) in Skies of Arcadia by how panicked or triumphant the music sounds.
Morrowind and Oblivion, in The Elder Scrolls series, switch to battle music whenever you initiate combat and whenever an enemy starts chasing you — regardless of whether you've spotted the enemy.
Same thing in Fallout 3 and Fallout: New Vegas, which are also by Bethesda. Players should especially take notice when the danger music starts up here, because a Deathclaw could be bearing down on you. Another caveat is that the Pip-Boy radio overrides the background music. The latter game also has creepy music when enemies are nearby but haven't detected the player yet, which transitions to the full-on battle music when they spot and attack you.
Read, THOSE GODDAMN CLIFF RACERS. Only in Morrowind though, but the ENTIRE Elder Scrolls community HATES them with the burning passion of a thousand suns, simply because they can see you from MILES AWAY and will follow you WHERE EVER YOU FUCKING GO. Once you either A) Leave the mountain range where they are, B) Get far enough away that they stop chasing you or C) Kill them, they stop following you (though option C is obvious).
The dragons of Skyrim are practically the spiritual successors to the cliff racers. And come with convenient pseudo-dramatic nordic chanting to let you know annoyance-from-above is on its way. While they're not so prone to chasing you across the land, trying to go about your business while a giant sky-lizard tries to burn you, your horse and all the NPCs in town to a crisp can be rather tiresome. The lack of acrobatics / jump spells / levitation in this generation doesn't make things any easier. Although once you learn the Dragonrend shout in a later phase of the main quest, you can force a dragon to land, which makes fighting them much easier (unless you are in a city, where the dragon tends to land several blocks away from you and take off by the time you catch up).
Left 4 Dead has musical cues for a lot of things. Zombie hordes attacking, special events, atmosphere cues, etc. Most prominent of all would be the leitmotif that kicks in when certain special zombies are nearby. And yes, people have already figured out how to replace said music with renditions of Yakety Sax.
Here are the Witch and Tank themes. If you hear them in gameplay, you know that you're in for a near-death experience.
The freeware PC game Survival Crisis Z varies the number of instruments used for its background music based on the number and type of enemies near the player, ranging from a simple bass beat to an almost-overwhelming cacophony of industrial, glass, and synthetic noise. Given that zombies can randomly appear en masse just by entering and leaving buildings, it's not at all uncommon to walk through a door and instantly know you're in trouble by virtue of several additional instruments kicking in.
Wonder Boy In Monster World was an exception to the boss rule: even the second stage of the final boss used one of the stock boss tracks, with original music only coming in for the end credits.
Uncharted: Drake's Fortune plays scarier action music when you go into fights. Since bad guys come in waves and sometimes hide in weird places, you can occasionally lose track of one or two enemies. Thankfully the music doesn't change back to the ambient sound effects until you've killed them all, so you know to use caution going around corners and such.
Super Mario Galaxy has an example heard in a few cases, there's a certain ominous theme appropriately titled "Danger Ahead" in the small section of the level before a boss battle, as can be seen when on the UFO before fighting Topmaniac, the small section of level before Tarantox and before the first King Kaliente battle (although really, it's kinda ironic the only bosses this happens for are those that don't need the warning because they're generally easy). Similarly, there's a kind of dead obvious giveaway of the boss battle about to start in Bowser Jr's reactor levels, in that his theme tune starts just before the boss starts attacking (and Bowser Jr himself will fly in and taunt you.)
"Danger Ahead" was remixed in Super Mario Galaxy 2, but it only played in Bowser Jr's Boom Bunker - which is a pretty ominous level in itself, featuring the wreckage of Megahammer, a castle with prison-style spotlights, a planet consisting of little more than a slew of spinning platforms and a black hole, a subspace swamp, and the sun as a massive fireball looming in the background.
The presence of enemies in F.E.A.R. and its sequel can often be given away by changes in the music and the occasional dramatic sting. Especially helpful for revealing Replica Assassins before they kill your face.
In La-Mulana, if you enter a boss room before unlocking the boss, the area music keeps playing. Once you unlock the boss, entering the room replaces the area music with the pre-boss music.
In Ace Combat 6, if the music stops without "Mission Accomplished" flashing on the screen, it is guaranteed that Strigon Team, cruise missiles, or both are going to show up in the next few seconds.
In the Tetris: The Grand Master series, if the music cuts out, the next section is going to have a Difficulty Spike. In TGM1 and TGM2's Master mode, this famously first happens at halfway through the game—once you get to the next section, pieces will start dropping instantly. In TGM3, this can happen as early as three-tenths into the game if you're fast enough
Plus many Original Generation characters have their own musical theme that plays when they take a turn in battle. Original enemies also have this, and it usually overrides the heroes theme. Take a good listen. If the music is inspiring or heroic, then they'll be pulling a Heel-Face Turn before the end. There's no way that "Trombe" or "I am Baran Doban" could belong to total villains after all. And Shura General Alion's joining of you would have come right the hell out of nowhere, since he didn't do this in the original game, were it not for his very non villainous music playing every time you fight him before hand. There are only two exceptions. Shu's sinister and epic "Dark Prison" is blaring whether he's shooting at you or saving your hide, and Alpha 3's Hazal Gozzo has the oddly cheerful "Clown Master" as his theme, despite being evil and never even has a chance to join you.
Most prominent example comes from Super Robot Wars W. The first Database member that appeared is Aria Advance, and her leitmotif, if listened closely, is a rearrangements of Kazuma's leitmotif.She is his clone.
In Alien vs. Predator 2, xenomorph encounters would be accompanied by the orchestral soundtrack...of AvP 1. For some reason the original installment, though packaged with a soundtrack, never utilized it in-game, which is why it is much, much scarier than the sequel.
This is also the reason that the actual film Alien cut back on its original bombastic musical score, replacing it with mostly silence.
The original score was cut back... but most of the film is actually scored. It's just so subtle and nuanced that it contributes to the atmosphere without you realising. It's still an aversion of the trope, just an aversion born of ridiculous amounts of compositional skill.
Aliens vs. Predator (2010) followed the example of its 1999 predecessor, leaving the score mostly unaltered except for certain scripted events. Arguably less effective, however, as the 1999 game used silence to emulate the score of Alien as described above, making it one of the creepiest games to date, matching the likes of Silent Hill.
Averted in Dual Orb II... for the simple reason that the developers didn't bother to make more than one battle theme for the entire game. Even the final battle uses the standard music.
In ICO, the music is your first warning that the shadow-wraiths are approaching, or that some are still lurking nearby even if you can't see them.
In Earthbound, you know a visit to the Threed Sunset Hotel is about to go very, very wrong when the usual hotel theme is distorted into an eerie parody of itself.
The music in Syndicate shifts to a much more tense and fast-paced theme when an enemy cyborg is nearby. The manual advises the player to use the music as an early warning system for imminent combat.
In Call of Duty: Modern Warfare 2, a deep note followed by ominous music means a Juggernaut is after you. Be very afraid.
Because Tomb Raider games tend to have ambient soundtracks for levels, musical cues become key means of distinguishing when a trap, puzzle, or hazard is nearby. And the more dramatic the cue, the more imminent the danger is (sometimes you will only have seconds to live unless you react quickly).
Dead Space. It's not over until the music goes away. This makes it rather disorienting to fight in a vacuum, where the battle music is typically absent.
Made even worse by the fact that the music seems to be stemming from the Necromorphs themselves. If you run away from a group of Necromorphs, you can hear the music slowly fade away as the distance between you grows larger and hear it slowly fade back in as the distance grows smaller, meaning that if you lose track of a Necromorph in a large area, you simply have to listen to the volume of the music to help clue you in as to whether or not you're getting closer.
In Metroid Fusion you can often tell that you're nearing a boss battle when a certain piece of ominous music plays. The soundtrack is non-apologetic about this, calling itself "Tension Before a Confrontation".
In Professor Layton and the Curious Village, the professor's theme has a subtle ticking as punctuation. This foreshadows the revelation that the villagers are all robots.
Averted when Layton's about to reveal something about the mystery, the music stops and says his stuff.
Mother 3 has one that, if you're paying attention to it, hints at the twist that Fassad is really Locria, the seventh and final Magypsy. When he confronts your party as 'New/Miracle Fassad,' the musical horns he now has fitted to him play an even further distorted version of the saxophone line in the Magypsys' leitmotif.
Additionally, all player characters and enemies have a certain instrument or sound (electric guitars, horns, animal noises, etc.) that plays when they attack, incorporated into the "sound battle" system. Because of this system, the player characters' combo instruments tend to stand out a bit more than the enemies', so it's easy to miss one of the first giveaways to the Masked Man's identity. When you first fight him, his combo instrument is the same as Claus's when he fought alongside you at the beginning of the game. In a similar fashion, knowing that Duster's combo instrument is a bass helps to remove any lingering doubt you might conceivably have as to Lucky's true identity, though this isn't as strong (or, indeed, as obscure) as the former example.
In Yoshi's Island, the room before (or with, in many cases) the boss always has the same ominous background music playing to indicate a battle will start. Comes with a long corridor for build up.
Both the Penumbra series and its spiritual successor Amnesia: The Dark Descent play this trope straight. Hide or run until the caution/danger music stops playing and the enemies are guaranteed to have left the area.
Used in many ways in the Silent Hill games. If you hear particularly ominous ambient noise/music, it usually means enemies are nearby or something big such as a Boss Battle or transition to the Dark World is about to happen. However, sometimes it's just a false scare.
Resident Evil 3: Nemesis: When "Feel The Tense" starts up, Nemesis has entered the area. In RE 2 and others, if the music is replaced by silence, it means something such as a Licker is going to jump out at you. In fact, more or less all the RE games use this trope in some way.
The more difficult bosses in Ys IV: The Dawn of Ys use "A Great Ordeal" for their battle theme, as opposed to "Battle 58".
In Ys VI, the music is silenced before the first boss appears.
In Iron Tank, the music changes to static noise, or sometimes the boss music itself, shortly before a boss fight.
In Syphon Filter, the music intensifies when the enemy is targeting you, and calms down when they lose sight of you. The later games such as Omega Strain have special music themes for high-ranking terrorists or Timed Mission objectives.
Mass Effect 1: It's not much of a spoiler, per se (talking to anyone suggests basically the same thing), but when the time comes to have it out with Wrex on Virmire, even walking towards him turns on the Ominous Drumroll.
Haunting Ground uses this specifically as a game mechanic: Belli castle has its ambient music, and it has the chase music for each of Fiona's pursuers. However, because those pursuers are actively searching for Fiona, they're running around the castle the same as she is. Whenever one of them is in a room adjacent to the one Fiona's in, the music slowly fades out into complete silence, leading to one of the best uses of "Wait, it's too quiet" ever to be visited on a player.
Appears accidentally in Dungeons of Dredmor. If the normal background music stops when you open the door to a room, instead of changing quickly when you walk through the door, it just means the game is having trouble loading both the massive amounts of enemies in the room and the awesome 'Monster Zoo!' theme.
In Hanako's bad ending of Katawa Shoujo, the ominous "Cold Iron" theme starts playing as the last scene begins, before things start going wrong.
Wrong for Hisao at least. Nothing could prepare the player for the awakening ofRage-Hanako.
The music in Battlestar Galactica Online picks up when you engage in behaviour that triggers the Threat indicator. Unfortunately, it's easy to trigger the indicator by accident.
Along with Wheatley's innocent-turned-sinister laugh, the ambient lighting turning red, and THE F**KING PANELS BOUNCING WHILE HE LAUGHS, the music suddenly becoming a lot more dramatic makes us realize that maybe it wasn't such a great idea to install him into GLaDOS's body in Portal 2.
Psychonauts. For just one or two seconds at a time in the BGM during the fight with the first brain tank, the BGM from Oleander's mind will suddenly play quietly, and then shut off again, cluing you in that he's behind it all. Although, you may have known already, and the full revelation does hit you in the face a few moments after the boss fight.
The music in Receiver changes and crescendos as you approach enemies.
In Xenogears, ''Light From the Netherword plays in the opening sequence, where a ship's systems mysteriously go out of control and result in its destruction. Omen, a remix of it, plays in Babel Tower when humans mutate into Wels, and other areas and events related to Deus and the Eldridge.
Live A Live subtly foreshadows that all the chapter bosses are one single demonic entity in the boss theme "Megalomania". The last 15 seconds of the theme before it loops are accompanied by an Ominous Pipe Organ, which seems out of place when fighting Wild West bandits and martial arts masters until The Reveal.
Slender: The Arrival does this twice. Once you get the third page, more ominous music starts playing and it increases as you continue to collect more pages. Later, after you activate two generators, strings start playing sinisterly and Kate the proxy starts chasing you.
Jet Force Gemini only has a single boss battle theme used for every boss. As such, this trope might appear to be played straight if you've only got as far as the first battle with Big Bad Mizar and are expecting the True Final Boss to have a unique theme, but since said final boss uses the same theme as all the others, it's technically a subversion. Even the final portion of gameplay that comes after the final boss reuses a common gameplay theme used in several previous areas too.
If you ever hear the 'Boss Intro' theme from Donkey Kong 64, then you can pretty sure trouble isn't far away. It works kind of like 'There Comes Trouble' from Banjo Tooie, and plays in many of the same areas (as well as the cutscene before the boss appears).
Conker: I don't think I like the sound of that music! Frankie: I don't think I like the sound of that music either!
Very subtle example in Bravely Default. The normal boss theme seems to be a standard looping track... but if you listen closely you'll notice that the second loop of the song has notably different backing, particularly the guitar riffs. This foreshadows the "Groundhog Day" Loop nature of the game, where the same events repeat with subtle differences each time.
The flashes are often made with music that has been public for a long time. Most of the time this isn't spoilery, as the music is straightforward - dramatic, sad, awesome, etc. However, in one case it was. The flash Jade: Wake Up begins with happy, joyful music reminiscent of the squiddles and appropriate visuals. People who listened to the Squiddles album before that, however, will know immediately that this won't last as the song later breaks down and turns into full-on Nightmare Fuel.
And then there's Intermission 2 which uses a previously released song entitled "English".
In certain games on Dasshutsu Game DERO!, just before a contestant fails the game, the soundtrack will usually culminate with an ascending "woosh" sound, followed by about a second of silence before the player's elimination. Except every so often, the show will also do this when a player has a close call but pulls through in the end.
Chrono Trigger has a funny pair of subversions involving Ozzie. The first time you meet him, he brings up a series of monsters with a crank, and they drop onto a conveyor belt. The battle music starts, and your characters even get into their battle poses... then the enemies fall into a pit at the other end of the conveyor belt. Insert "record winding down" sound here. Then, the second time you meet him, the boss theme starts playing, and then a small cat comes in and trips a lever, and the boss theme fades out as Ozzie drops into the Bottomless Pit.
And who can forget Dalton? When he epically turns the Epoch into the "Aero-Dalton Imperial", Crono's "fanfare" theme starts up, prompting Dalton to yell, "No, no, no, no...! Stop the music!" The music then changes into "A Spot of Crisis", a tense theme, and he says, "Ha! There we go! Ready for takeoff!"
In the Greenwood area of Soul Blazer, there is a dog who, when talked to, will tell you that "today's special is...you!" accompanied by an abrupt end to the background music. The dog will then proceed to explain that he was only joking, and the background music starts up again.
In Shining in the Darkness, despite the fact that the fight against The Dragon had a special boss theme, the final boss uses the normal combat theme you've heard all game. That is, until he gets serious...
With the exception of the final boss, of course, who gets his own unique remix of Twister. Every other non-boss battle randomly uses music.
The first Xenosaga game uses the same battle music for every fight. Common enemies and bosses have the same tune. The sole exception is the final boss, who has its own theme.
Scratches subverts it near the beginning, on the first time you go down to the basement, creepy Psycho-like strings start playing giving you the feeling something is gonna jump at you from the shadows at any moment, this effect makes you want to leave that place as soon as possible. Later its played straight when for looking for Catherine Blackwood's corpse on the yard the music changes when you happen to dig on the right spot, also on Last Visit after solving all puzzles the music changes to the same creepy strings heard on the basement hinting of the scare lurking nearby.
In the arcade version of Super Contra, the penultimate boss gets its own theme, but the final boss just uses the main stage music.
In Mega Man 2, the final boss against the alien hologram has the same music as every other boss.
Mega Man X Command Mission pulls a nice trick coupled with Disc One Final Dungeon in Chapter 9 with Epsilon. He gets his own battle theme—two, in fact—and his fight is insanely tough. One may think that since his music was so different he was the Final Boss... until you notice that the game hasn't ended, and you haven't gone through the series' trademark Boss Rush yet.
In Season 11 of Red vs. Blue, someone fires a gun into the air to disrupt a standoff between the Reds and Blues. Everyone turns to look and Tex's Leitmotif is played. It's Donut.
The Simpsons had it in the episode "The Springfield Files" (Fake Crossover with The X-Files) when a mysterious music cue is revealed to be coming from a passing bus in which an orchestra is playing.