->''"Rhythm is the key\\
as you open up the door"''
-->-- '''Hive''', ''Ultrasonic Sound''

Using music and musical instruments as security measures. Pianos or similar instruments are common, as you are dealing with keys. Can often be the way to conceal your secret lair by being HiddenInPlainSight. The tune itself may be significant/ironic, or the [[ThemeTuneCameo Theme Tune]] or {{Leitmotif}} of a character.

Subtrope of SolveTheSoupCans. Compare with MusicalTrigger. Can be related to OnlySmartPeopleMayPass, if actual musical ability is required.
SisterTrope to OpenSesame, when the password is a spoken phrase.



[[folder:Anime and Manga]]
* In ''Anime/MaiOtome'', a specific song, from which each of the three main characters knows one verse each, is one of the three requirements for activating [[spoiler:the Harmonium]].

[[folder:Comic Books]]
* In one issue of ''Comicbook/TheIncredibleHulk'' the Leader's time machine is programmed by playing a piano keyboard.
* In a ''[[ComicBook/DisneyDucksComicUniverse Scrooge McDuck]]'' story by Carl Barks that's a riff on ''The Hunchback of Notre Dame,'' Scrooge programs his vault so that it can only be opened by playing "My Bonnie Lies over the Ocean". Trying to protect his secret by using a wishing well (ItMakesSenseInContext), he inadvertently reveals it to the hunchback (who lives near the bottom of the well scooping up the coins people throw in and eavesdropping on their wishes in the process), which kicks off the plot.
** A ''Ducktales'' comic written for ''Disney Adventures'' had a similar plot, in which Scrooge has a voice-activated lock to the vault on his money bin which only opens when it hears him singing the opening lines of "Comin' Through the Rye". And the Beagle Boys just so happen to have a cousin, Baritone Beagle, who's good at impressions...
* In one issue of ''Comicbook/MuppetBabies'', the group imagines that the world is running out of music. In their imaginations, it turns out that it's being eaten by the Note-All, with approval from Piggy, who wants ''her'' music to be all there is. His ''staff'' puts the ''rest'' behind ''bars''. When the Note-All eats Piggy's singing, as well, she decides to go free her friends. When physical keys don't unlock the bars, Rowlf suggests a ''musical'' key. When Piggy hits high C, the bars open.
* One shows up in Creator/WarrenEllis' ''Comicbook/IgnitionCity'', triggered by the owner's favorite song - "[[http://www.youtube.com/watch?v=kyofs0mreCc A Nightingale Sang In Berkeley Square]]".
* In the 60s ComicBook/{{Archie}} story "That Way Out Sound", Mr. Lodge shows off a vault with a door that can only be opened by the "unearthly, weird, way-out sound" produced by a one-of-a-kind tuning fork. Unfortunately, Archie accidentally locks him inside the vault, tuning fork included. A variant ensues as Archie and his friends free him by reproducing the "way-out sound" with their rock band instruments; it turns out there's no sound the Archies ''don't'' hit sooner or later.

[[folder:Films -- Animated]]
* ''WesternAnimation/MonstersVsAliens'': The security lock to the central core of Galaxar's ship is protected by a musical sequence which seems to be right out of ''VideoGame/DanceDanceRevolution''.
* ''WesternAnimation/DespicableMe2'': The entrance to El Macho's lair is protected by the tune of "La Cucaracha." HilarityEnsues as Gru tries to play the tune and his nacho sombrero hinders him every step of the way.

[[folder:Films -- Live-Action]]
* ''Film/JamesBond''
** In ''Film/{{Moonraker}}'', access to Drax's base is controlled by a musically coded keypad. The tune is the same five notes used to communicate with the aliens at the end of ''Film/CloseEncountersOfTheThirdKind''.
** In ''Film/ForYourEyesOnly'', the Identigraph room in Q's lab has a musical lock. The 7-note key is the title passage of "Nobody Does It Better" from ''Film/TheSpyWhoLovedMe'' (2 films earlier); it is less obvious, though, because Q stops after 5 notes and Film/JamesBond fills in the final 2 a few seconds later.
* In ''Film/TheGoonies'', a creepy pirate organ opens a door or collapses the floor depending on whether you play the right tune or not.
* In ''Film/BatmanBegins'', the Batcave is accessed from Wayne Manor by playing a specific sequence of keys on the piano. This is carried over to ''Film/TheDarkKnightRises''. It does not, however, happen in ''Film/TheDarkKnight''; a different "Batcave" is in use in that film, due to Wayne Manor being under reconstruction.
* ''Film/WillyWonkaAndTheChocolateFactory''. In Willy Wonka's factory, the door to enter the Chocolate Room (with the chocolate river) had a musical lock. The tune for the lock is the Overture from "The Marriage of Figaro," by Mozart, ''not'' Rachmaninoff, as [[KnowNothingKnowItAll Mrs. Teevee]] claims.
* The film adaptation of ''Film/RichieRich'' had this with the parents unlocking the family vault by singing along with the code tune, "Side by Side", as a duet. The villain was not amused.
** The lock stops recording after the first line, "Oh, we ain't got a barrel of money," which means that this is the actual key (as ironically befits a massive vault [[spoiler:that contains valuable mementos, not real valuables]]). The parents only sing the rest of the verse out of nostalgia and [[SickeninglySweethearts a need to be saccharine]].
* The movie ''Film/WarGames'' has the main character locked in a holding cell. He gets out by recording the musical tones from the keypad to his cell and playing them back from a microcassette recorder.
* In ''Film/HudsonHawk'', the villains use a ridiculous-looking set of handcuffs with colour- and sound-coded buttons. Which makes it trivial for Hawk to get out of them (in fairness, it's probable that they intended him to escape eventually).
* In ''Film/{{Prometheus}}'', the Engineers' ship is activated by pressing buttons in order and by playing notes on a flute-like instrument.

* Pops up ''everywhere'' in Sharon Shinn's ''Literature/{{Samaria}}'' series. All angels are born with perfect pitch and singing voices, with which they can pray for all manner of divine intervention - rain or sunshine, cures for plagues, or even a good old-fashioned smiting. Meanwhile, enterprising mortals have come up with musical locking boxes and other such aural toys. The theme of musical control is so heavily emphasized that the nature of the Samarians' god winds up being something of an UnReveal.
* A shortcut to Abhorsen's House in ''Literature/{{Sabriel}}'' will only open to the sound of Mosrael, a bell which is otherwise never used in the series (it sends the ringer into Death).
* In book two of ''Literature/The39Clues'', the search for the Clue eventually leads Amy and Dan to [[spoiler:the house of a man named Fidelio Racco; specifically, a keyboard in his house that Mozart played. Playing a certain song (a unique version of Mozart's "KV 617" left in the Parisian Catacombs centuries ago) on this keyboard causes a trapdoor in the floor to open, revealing two swords made of a tungsten alloy, tungsten being the Clue.]] The trigger even works when [[spoiler:a booby-trapped key ''causes the instrument to explode before the song can be finished''.]]
* In ''Killashandra'', part of Creator/AnneMcCaffrey's ''Literature/CrystalSinger'' series, the lock hiding the illegal computer equipment inside the organ is opened by playing a (supposedly) original melody. Fortunately, the protagonist knows Beethoven's fifth symphony, and can play the opening line "accidentally" while tuning it.
* John Galt likes using a sound lock to protect things he doesn't want outsiders to see in ''Literature/AtlasShrugged'', although it's not sung. Backed up with SelfDestructingSecurity for anyone who tries to force their way in.
* As captured Literature/JamesBond in ''Literature/DevilMayCare'' is sent for a mission to Afghanistan on the behalf of the BigBad, he and Chagrin come across a vault door which requires a code to be opened. Each press for a five-digit code that opens it emits a sound of its own, and Bond memorizes it to teach it to his fellow prisoner Scarlett.

[[folder:Live-Action TV]]
* ''Series/StarTrekTheOriginalSeries'' episode "The Paradise Syndrome". The obelisk left by the {{Pre|cursors}}servers had a door that opened in response to a specific sequence of sounds (musical notes or speech tones).
* This was done in the season 3 finale of ''Series/{{Lost}}'': Charlie had to enter a code to the tune of a Beach Boys song to unjam the signal going out from the island.
** ''Good Vibrations'', to be specific.
* In "Suckers," an episode of ''Series/{{CSI}}'' they investigated the robbery of a hotel vault. At the end Grissom realises that [[spoiler: the lock was programmed so the tones of the numerical keys would tap out the melody for "Three Little Maids From School" from ''Theatre/TheMikado''. A tune that would be familiar to the thieves; the manager was co-operating with them to carry out an insurance scam]].
* In one episode of ''Series/KyleXY'' Kyle and Jessie called Kyle's girlfriend to get her to play a song that opened a lock.
* In ''Series/DoctorWho'', "[[Recap/DoctorWho20thASTheFiveDoctors The Five Doctors]]", the fifth Doctor played a harp to get into the villain's lair. The tune itself was HiddenInPlainSight.
* In ''Series/StargateAtlantis'', Janis, an Ancient scientist, used three different tones played in order to hide his secret lab.
* The first season of ''Series/TheMole'' ended with a complex, multi-part puzzle that involved one of the remaining contestants stuck in a locked room with a xylophone and sheet music. The door would only open if he could play "Mary Had a Little Lamb"... and he couldn't read music.
* There's an episode of ''Series/MacGyver1985'' ("The Heist") featuring an ultra-high-tech (for the time) lock which requires four tones emitted by a remote control. This being [=MacGyver=], he improvises by playing some wineglasses.
* In the ''Series/WhiteCollar'' episode "Empire City", the safe in the Cotton Club opens for a few bars of the jazz classic "Harlem on my Mind" as sung by the proprietor. Neal sneaks a vinyl recording of this music past the metal detector in order to open the safe.
* An episode of ''Series/{{Chuck}}'' involved a hidden compartment opened with a high C note. [[spoiler:Casey uses his choir-boy background to produce the note.]]
* ''Series/MurderSheWrote'': In "A Murderous Muse", the killers set up a system whereby when the VictimOfTheWeek plays a certain chord on the piano, it unlocks the secretary behind him and fires the gun hidden within.
* ''Series/WonderWoman''. In the 1st season two-part episode "Judgment From Outer Space", Wonder Woman meets a space alien named Andros. During Part 1 she hears him whistle a six note musical phrase, and in Part 2 she uses that same phrase to both open the outer hatch on his space ship ''and'' deactivate a force field inside the ship.

* One ''Radio/AdventuresInOdyssey'' episode had the characters facing an organ with the clue to "Start in the center and play 'a deaf cabbage.' Robin has had music lessons, so she realizes that the phrase can be played on the organ and does so, opening a hidden door.

[[folder:Tabletop Games]]
* ''TabletopGame/DungeonsAndDragons''.
** 2nd Edition AD&D adventure [=OA6=] ''Ronin Challenge''. The Su-Rai Vault has a dangerous gas trap. One of the doors in the vault is covered with the notes of a simple tune. If a {{PC}} with the Singing or Music proficiency sings the tune or plays it on a musical instrument, the valve that releases the gas trap will stay sealed for 24 hours, allowing the {{PC}}s to explore the vault without being gassed.
** The 3rd Edition Dungeon Master's Guide mentioned a note played upon a lute as a possible key to open a magical door.

[[folder:Video Games]]
* One early area of ''VideoGame/AnotherCode'' has you play the piano to open a secret passage, and later using a music box to open a fireplace passage.
* ''VideoGame/ResidentEvil'' has a piano you play Beethoven's "Moonlight Sonata" on to unlock something. Jill knows piano; Chris has to find Rebecca.
* At one point in ''VideoGame/TheNeverhood'', you have to open a door by spitting into a SeriesOfTubes to make them whistle the same tune as another series of tubes.
* ''VideoGame/TheLegendOfZeldaOcarinaOfTime'', taking from a few earlier games, has several dungeons that you unlock by playing different songs on your ocarina.
** Also playing the Song of Time will move some blocks that have the Door of Time's symbol on it.
** They are all a character or area's {{leitmotif}}... For example, the Sun's Song is the ''sun's'' leitmotif; it plays whenever the sun rises [[spoiler:and the sun rises whenever the song is played]].
** And ''VideoGame/TheLegendOfZeldaMajorasMask'', its direct sequel as well.
** And ''[[VideoGame/TheLegendOfZeldaTheWindWaker Wind Waker]]'', where the notes are conducted on the titular baton.
** Averted in the sequel, ''[[VideoGame/TheLegendOfZeldaPhantomHourglass Phantom Hourglass]]'', where there is no instrument whatsoever. The third game, ''[[VideoGame/TheLegendOfZeldaSpiritTracks Spirit Tracks]]'', however, makes up for this with the Spirit Flute, which utilizes the DS microphone. Playing duets with the Lokomos help restore the Spirit Tracks, which enable you to go to new areas.
* ''VideoGame/PrinceOfPersiaTheSandsOfTime''. In the GBA version, there are several levels that are passed by playing a certain tune in a certain sequence.
* In ''VideoGame/FinalFantasyII'', the entrance to Kashuan Keep can only be opened by the voice of a member of Kashuan's royal family or the ringing of the Goddess's Bell.
** ''VideoGame/FinalFantasyVII'' has the final LimitBreak for Tifa that is obtained by playing the right notes on the piano.
** ''VideoGame/FinalFantasyVIII'' has an organ that needs to be played to open a gate.
** A dungeon in ''VideoGame/FinalFantasyIX'' has bells as InterchangeableAntimatterKeys.
** ''VideoGame/FinalFantasyX2'' has a puzzle involving repeating notes.
* In ''[[VideoGame/BaldursGate Baldur's Gate: Dark Alliance II]]'', you have to open a secret passage by playing a harpsichord.
* ''VideoGame/BrutalLegend'' has various Guitar riff sequenced that activate certain powers, up to and including opening new areas.
* In ''VideoGame/{{Outcast}}'' you had to put the right pipes (as in flute pipe) into the right sockets on an altar (or something) to play a certain melody. After accomplishing this, you'd get another key for something else...
* The Selenitic Age Descriptive Book in ''VideoGame/{{Myst}}'' is accessed via a five-note combination. Then to enter TheMaze, you have to play the five ambient sounds in the proper order. Furthermore, the sounds in the maze indicate the compass direction you need to go.
** All the ''Myst'' games seem to have at least one sound puzzle each. In ''VideoGame/{{Riven}},'' the combination to unlock Catherine's cell is revealed by listening to [[spoiler:Gehn's watch]].
** ''Riven'' also has the overarching animal-sounds puzzle that is scattered across the islands. There are five balls with a D'ni number carved in them, and each makes a Riven animal sound when spun (using at least one fictional animal.) The code makes perfect sense, as it would only be understandable by someone well-versed in both Riven and D'ni culture (it was intended for Atrus, but the player [[GuideDangIt will figure it out eventually]].)
** ''Myst IV'' involves using Sirrus' Spider Throne to vibrate four different pieces of minerals, so that all of them being pushed out of their literal "locks" deploys a bridge [[spoiler: to a bomb factory.]] The musical element comes from the tones Spire's crystals give off when their electrical charge fades, which the Throne channels via huge cables within the Age.
* The drawbridge passtune in ''VideoGame/NetHack''. You find it out by either playing Mastermind or by having your god tell it to you.
* ''VideoGame/{{Loom}}'s'' MagicMusic starts you off with the "Opening" draft, which works as a universal one of these (where [[ThePasswordIsAlwaysSwordfish The Password Is Always]] E-C-E-D).
* There are a couple of puzzles in ''VideoGame/LufiaIIRiseOfTheSinistrals'' where you have to step on "musical note" tiles in a certain order to open the locked doors.
* ''VideoGame/{{Startropics}}'' has a giant organ with eight keys, representing the notes of a musical scale. The solution comes from a parrot that says "Do me so far, do me?" This, of course, means playing "Do Mi So Fa Do Mi" on the organ.
* ''VideoGame/WonderBoyInMonsterWorld'' requires you to remember short ocarina sequences to open the doors in the first dungeon.
* ''VideoGame/EternalDarkness: Sanity's Requiem'' has you play one song three times: twice on an organ, once on a piano.
* ''VideoGame/TheSeventhGuest'' has one [[http://www.youtube.com/watch?v=9nSDedyBnzg&feature=search shown here]] involving a piano. Technically, though, it's more of a Simon Says puzzle in this case.
* One of the adventure games in the ''Trapped'' series (not ''VideoGame/TheTrappedTrilogy'', the ''VideoGame/TrappedSeries'') requires you to play the tune from a music box on the piano to open a secret door.
* Such a puzzle exists in ''VideoGame/SilentHill1'', the only clue being a poem about birds (and interestingly, the correct solution produces no music because the keys you have to press are all broken). A puzzle involving a child's toy piano with pictures of birds on it appears in ''VideoGame/SilentHillShatteredMemories'', as a ShoutOut to the original game.
* You don't actually have to solve a puzzle, but in ''VideoGame/ChronoTrigger'' playing an organ always reveals hidden doors.
* In ''VideoGame/ChronoCross'', each element has a unique tone when cast in battle. Playing [[spoiler: the Song of Life]] with these tones when fighting the FinalBoss will instantly win the battle and free [[spoiler: Schala from Lavos]]. This unlocks a better ending than the player would get by killing the boss.
** Being able to pull it off successfully is hard because the boss can interrupt (or help) the melody with his own magic.
* ''VideoGame/LunarTheSilverStar'' has a duet between true lovers as the key to one dungeon. A long-distance duet between the leads opens it. Kyle and Jessica make for a DreadfulMusician duo, while Nash is too worried about stepping on Mia's notes to harmonize.
* ''VideoGame/IllusionOfGaia'' requires protagonist Will to play specific tunes on his flute to open several gates.
* ''VideoGame/PhantasyStarII'': In order to get the card keys to open the Dams, you need to play a keyboard, however you must learn the Musik skill to even be able to play the keyboard.
** At one point, you ''trade away'' one of the songs you no longer need. ...zah?
* ''VideoGame/EternalSonata'' has you play increasingly long portions of [[spoiler:Chopin's "Nocturne"]] on a large piano in order to progress through the Xylophone Tower of the Shining Keys. It doesn't unlock door or gate, but it does cause a sloped ramp to appear each time.
* Frequently in ''VideoGame/ZorkNemesis'', since the element of water is associated with music and the alchemist of water was a music teacher. The first one is a fountain which can be opened by turning on streams of water which correspond to the notes in a melody played on pan pipes.
* Near the end of ''VideoGame/GodOfWarIII'', there's a puzzle that doesn't even bother trying to hide what it is, as the "notes" are copies of the PlayStation's four main buttons and the tune you play is the franchise's {{leitmotif}}.
* ''VideoGame/{{Fallout 3}}'''s quest Tranquility Lane, set in a LotusEaterMachine, has a possible ending where the player character can activate the simulation's failsafe by reproducing the ubiquitous {{Leitmotif}} on a collection of tuned household items.
* In ''VideoGame/FalloutNewVegas: Dead Money'', you have to play Vera's song holotape to unlock the vault elevator (or have Christine say the password with her new voice), after retrieving the music tracks from the receptionist terminal.
* In ''VideoGame/TheLostCrown'', Nigel must repair a church organ and then play a specific sequence of notes to banish an evil ghost which blocks his path to a vital clue.
* ''VideoGame/KingsQuestIVThePerilsOfRosella'' features an organ at the top of a tower in a haunted house. The organ has a secret drawer in it, which opens if the organ is played correctly (Rosella has to find the sheet music first).
** ''VideoGame/KingsQuestVIIThePrincelessBride'' has another music puzzle in Etheria involving a harp, which will transport Valanice to a sort of pocket dimension where she can speak with the Three Fates if she plays the right notes on it. The clues to the notes are given by the faerie dragons flitting around in another area of Etheria.
* One way of getting control of the Nautilus in the game ''VideoGame/ReturnToMysteriousIsland'' involved playing a few bars of music solely on the black keys of the Nautilus's organ (as, apparently, Captain Nemo specialized in playing music that required only the black keys).
* ''VideoGame/{{Seiklus}}'' uses a giant piano. The keys are colored, and you have to jump on them in a sequence [[EnterSolutionHere found elsewhere.]]
* ''VideoGame/DreamChronicles'' series loves "repeat the sequence" puzzles involving pressing the keys of some musical instrument (even if it's just the key order you have to memorize, not the tune itself - you can see which keys are being activated).
** The original game has the piano room, where clicking portraits on the wall will produce different tunes for you to repeat; completing them all opens the door to the outside.
** The second game has the organ room, where you need to repeat several tunes in order to unlock the passage to the second floor. Another floor has a puzzle requiring you to put several musical instruments in proper order, indicated by a book found in the library.
** The third game has another organ-like instrument, where the same sequence-repeating type of puzzle protects several items you need to obtain.
* The FMV ''Lawnmower Man'' game has a very basic Simon-like musical keyboard level, but it takes forever to watch the player character enter the code after you do.
* In the text adventure ''AugmentedFourth'', the player character has occasion to play a piece called "The Well-Tampered Xylophone", which consists of exercises in "twenty-five keys". The extra one turns into an actual key.
* Most of the time in ''VideoGame/{{Aquaria}}'', Naija uses her songs to [[VoluntaryShapeshifting change into a form]] that is best suited for passing a certain obstacle, i.e. using the Beast Form to swim past strong currents. However, there are a couple of cases where just singing is enough to remove an obstacle, such as the door in the Song Cave, the whale in The Abyss, and [[spoiler: Li's cage near the end of the game]].
* In the ''Bloodmoon'' expansion for ''VideoGame/TheElderScrollsIIIMorrowind'', the Ritual of Earth requires you to listen to a set of geysers from some stalactites and then activate the stalactites in the same order.
* The main objective in ''VideoGame/ImpossibleMission II'' is to collect six pieces of a song (two of the eight pieces are duplicates) that unlocks the express elevator to the penthouse control room.
* Several times in the ''VideoGame/{{Ultima}}'' series, the Avatar has to play a simplified version of the song 'Stones' in order to gain a PlotCoupon or MacGuffin.
* ''VideoGame/TheJourneymanProject 3'' has a set of Buddhist Prayer Wheels on which the player must playt a prayer chant. [[spoiler:One of them is squeaky and must be oiled first.]]
* ''VideoGame/SchizmMysteriousJourney'' runs in a similar vein as the above, with a set of Argilan prayer grinders. After an alien priest shows up and speaks a string of words that open a hidden door, you have to play it back using these devices.
* ''VideoGame/AlidaTheEnigmaticGiant'' takes this UpToEleven. Vaults scattered around the island are fitted with sensitive microphones which pick up the sound from the island's massive, fully functional electric guitar. Each and every component of the guitar must be set correctly - and that includes the peghead, switch, and potentiometer dials, before the guitar's sound can open the doors, [[spoiler: provided a designated door has been primed to receive the sound, that is.]]
** However, this is made somewhat UnwinnableByDesign in the fact that almost none of these devices tell you if you've set them correctly, and even the strings don't sound any different after they've been properly tuned by the peghead.
** The same game also has a small keyboard of tubular bells that unlocks the tram to the Switch, which Arin gives you the code for. ([[GuideDangIt That is, if he's met you and you've tried playing that thing first.]])
* ''VideoGame/NancyDrew:The Deadly Device'' includes a puzzle where you have to first build a circuit board for a small tesla coil, and then program it to play a series of notes [[spoiler: revealed in Niko's notebook]]. Amusingly, you get an award for making the coil play actual music. Bonus points that this is a real life thing, called a "Zeusaphone".
* ''VideoGame/{{Safecracker}}'' has a fairly easy puzzle in the Crabb & Sons mansion/office's music room, used to unlock a well-hidden safe inside a piano. The code is the first 14 notes of Twinkle Twinkle Little Star.
* An optional puzzle in ''VideoGame/{{Undertale}}'' features this, where you must play the first few notes of a tune heard in a room a little bit ahead on a piano. [[spoiler:The reward's only barely worth it, though.]]
* ''VisualNovel/NineHoursNinePersonsNineDoors'': Unlocking the exit door to the First Class Cabin requires playing a piano. After collecting the sheet music, it's revealed that the piano is tuned incorrectly, so the actual puzzle is matching the proper notes to their altered locations. It's actually one of the easiest puzzles in the game, as the set of keys you're able to choose from is quite small, and after playing the first line correctly, the game completes the rest of the song for you. Notable in that the piece of music played isn't a character theme, scare chord, or in any way related to the game's soundtrack, but the Westminster Chimes. This prompts a comment from one of your companions as to Zero's motives and nothing else.
* Getting through one BonusDungeon in ''VideoGame/CosmicStarHeroine'' requires playing a sequence of notes on a piano. In practice this is a simple LockAndKeyPuzzle as you don't personally choose any notes, you simply need to find a piece of paper and then get to the piano.

* The ''Webcomic/MSPaintAdventures'' series ''Webcomic/ProblemSleuth'' has the same puzzle as ''VideoGame/ResidentEvil'' as a ShoutOut. It also [[ZigZaggedTrope plays with]] this trope by occasionally ''literally'' using musical instruments as security measures (eg. wedging a door shut with an oboe) - [[http://www.mspaintadventures.com/?s=4&p=001649 at one point]] "security measures" is even {{Pot Hole}}d to a Google Image Search for "woodwind instruments".

[[folder:Web Original]]
* In the ''WebVideo/{{lonelygirl15}}'' story "lonelygirl15 Season One Finale", the door to the Order base would only open if certain musical notes were played in sequence.

[[folder:Western Animation]]
* In ''WesternAnimation/XiaolinShowdown'', the vault for the [[MacGuffin Shen Gong Wu]] is opened by playing specific notes on wind chimes.
* In the ''WesternAnimation/SouthPark'' episode "Towelie", Towelie attempts to remember the code to enter the "Secret Government Base". The buttons make a noise as they are pressed and Towelie plays the tune to "Funky Town". Which doesn't open the door.
** The episode "Imaginationland" uses this as an OverlyLongGag.
* ''WesternAnimation/BatmanTheAnimatedSeries'':
** The episode "The Cat and the Claw" featured one of these where the keys of a piano had to be pressed in the right order - the first few bars of Beethoven's Ode to Joy - to open a secret door. [[spoiler:Catwoman, having had piano lessons, played that out with ease and then continued...showing the hidden parts of the room.]]
** Another puzzle, this one courtesy of the Riddler, featured a door and three keys, labelled "A", "C" and "D". Trying either the "A" or "D" key releases a few giant circular blades at the would-be solver, but the key of C? No sharps.
* ''WesternAnimation/ScoobyDoo'':
** One episode involved an organ, and the phrase "feed the organ" to open a secret passage. Which was also the sequence, "F", "E", "E", "D" keys.
** Another episode, "Phantom of the Country Music Hall," had a musical code "FEBAG" that opened a secret passage. And yet another episode had the villain's name, Ace Decade, spelled out in a piece of sheet music. ScoobyDoo ''likes'' this trope.
* Appears prominently in the ''WesternAnimation/TaleSpin'' two-parter "For Whom the Bell Klangs". The ancient civilization of [[MeaningfulName Tinabula]] based all its technology around sound, including [[spoiler: the sonic superweapon that [[BigBad Klang]] is after, as well as the city's self-destruct mechanism]]. Unsurprisingly, they encounter a door early on that is meant to open with a precise musical note: archaeologist Katie Dodd has the perfect pitch necessary to open it, but the hapless mook who tries first isn't so lucky.
-->'''Klang:''' "[[{{Pun}} She said 'B', not 'B Flat']]!"
* In the ''WesternAnimation/FostersHomeForImaginaryFriends'' episode "The Big Cheese", no one knows the combination to disable the new security system. No one, that is, except Cheese, who is singing the beeps the keypad made when it was entered. HilarityEnsues as the others try to figure out the combination one note at a time.
* An episode of ''WesternAnimation/JimmyTwoShoes'' had Heloise enter her secret lab in the AbsurdlySpaciousSewer by tap-dancing in rhythm on a manhole.
* ''WesternAnimation/JosieAndThePussycats in Outer Space'', episode "The Hollow Planet". A prison door unlocks when a whistle with a specific pitch is blown twice.
* ''WesternAnimation/AlvinAndTheChipmunks'' once got press-ganged into traversing an ancient temple, with traps that get disabled through singing. It seems, though, that any song will do as long as it's in chipmunk voices, since a second group of chipmunks go through it later by singing a completely different song than Alvin and his brothers did earlier.
* In ''WesternAnimation/ScoobyDooMysteryIncorporated'', Mr. E opens his vault by playing the first few notes of his signature theme.
* The ''WesternAnimation/StevenUniverse'' episode ''The Test'' has this in Pearl's room, where Steven must step on four lights in the correct order to open up the stairs. Afterwards, he must then dodge swinging axes. When Steven found out that Garnet's room was rigged, Steven returned to Pearl's room, where he found out that the axes phased through him, and that the same panels always allowed the stairs to open regardless if he stepped on the right panels or not.
--->'''Steven:''' It didn't even matter?!
* An episode of ''WesternAnimation/TheSimpsons'' which parodied ''Literature/TheDaVinciCode'' features Lisa on a hunt to find a mysterious treasure guarded by an order of nuns. A clue to the treasure informs seekers to devote themselves to God with "heart and soul"; Lisa realizes that this is a reference to the song of the same name and plays it on the convent's organ, activating a RubeGoldbergMachine that reveals the next part of the puzzle.

[[folder:Real Life]]
* Averting this trope in RealLife is why tonal keypads at [=ATM=]s ''don't'' use different pitches for each number, preventing eavesdroppers from copying other peoples' [=PIN=]s by sound.
* If you use a phone number a lot, eventually you'll be able to tell if you've entered a wrong digit by sound alone.
* The earliest hackers (known as Phreakers) would use a tone of 2600 Hz which caused a telephone switch to think the call was over, leaving an open carrier line which could be exploited to provide free long-distance and international calls.
** The tone was discovered in approximately 1957, by Joe Engressia, [[DisabilitySuperpower a blind seven-year old boy. Engressia was skilled with perfect pitch, and discovered that whistling]] the fourth E above middle C (a frequency of 2600 Hz) would work.
** For extra fun, [[FreePrizeAtTheBottom free whistles given out in Cap'n Crunch cereal boxes]] also produced a 2600 Hz tone when blown.