Since it's one part VisualNovel, ''VisualNovel/NineHoursNinePersonsNineDoors'' is sure to have some of the wonderful music that's usually seen in that genre. Here are samples of some of them.
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* [[http://www.youtube.com/watch?v=rA_DvZ8kQRc Quietus]]: The '''Bad End''' game over music. Starts off with a demented chime, then morphs into a metal, slightly industrial tune.
* [[http://www.youtube.com/watch?v=9GLYF5O1gMY Chill and Rigor]]: Reminiscant of Hello Zepp in ''Franchise/{{Saw}}''.
* [[http://www.youtube.com/watch?v=raQ8ATBniAQ Recollection]]: The piece from the moment in the [[spoiler: "Submarine" ending when June talks to Junpei before dying in his arms]]. It also plays in the True ending when [[spoiler:Clover and Snake reunite at the chapel [[note]]in that case it's 100% heartwarming, unlike the bittersweet June-Junpei scene[[/note]]]]; and in the Safe ending when [[spoiler:June gives Junpei her final words before disappearing from existence [[note]]it's made more bitter and confusing thanks to Zero's final speech[[/note]]]].
* [[http://www.youtube.com/watch?v=0CcFdLk6oF4 Octal Game]]: A much more relaxing piece, contrasting the rest of the tracks tense feelings.
* [[http://www.youtube.com/watch?v=EjQfY47pFNs Morphogenetic Sorrow]]: A track that clearly tells you that this is the finale. The fact that it plays in [[spoiler: [[SoundtrackDissonance the Sudoku puzzle]]]] really changes the mood. A remix of it acts as the backbone of the [[http://www.youtube.com/watch?v=ZAqGs441qzU trailer music]] of the sequel.
* [[http://www.youtube.com/watch?v=9xJSPwvhjL4 Foreboding]]: A track that's reminiscent of [[VisualNovel/UminekoWhenTheyCry goldenslaughterer]], giving quite an intense atmosphere.
* [[http://www.youtube.com/watch?v=8nVkPZOyzBE Unary Game]]: Guaranteed to induce panic.
* [[http://www.youtube.com/watch?v=9HzQzkXjIRY 9 Years]]: The music that plays during the true ending/prologue. Also counts as Crowning Music of Heartwarming due to the bittersweet finale.
* [[http://www.youtube.com/watch?v=I8HRjFRRf4E Ternary Game]]: An oddly energetic track compared to the rest of the soundtrack.
* [[http://www.youtube.com/watch?v=otY4bLTJL9k Septenary Game]]: A catchy track that is somewhat upbeat with a tinge of melancholy. It plays in the operating room (Door 7) and [[SoundtrackDissonance the shower room (Door 3) that contains the grisly remains of]] [[spoiler:Nijisaki]]. A nice break from the usual ominous music.
* [[http://www.youtube.com/watch?v=W1CveYZh1OM Nonary Game]]. Appropriately for a track that uses the name of the game the characters are themselves stuck in, it plays during the FinalExamBoss room, and it has the feeling of a "final boss". [[spoiler:Even though there's actually one last puzzle beyond this room.]]
* [[http://www.youtube.com/watch?v=Fqpa9GFQmLU Senary Game]]: An extremely dark, yet pumping track playing in several later rooms, setting the mood with its sinister torpedo-shot synth.
* [[https://www.youtube.com/watch?v=l7W7NFPv6sY Binary Game]] plays in the 1st and 2nd Class Cabins, and it's a chipper tune that screams anything but darkness. Contrasts with "Unary Game" a lot.
* [[https://www.youtube.com/watch?v=ai8eWvCYkB0 Extreme Extrication]] excels at giving the "escape from the sinking ship" feeling. Very iconic song of 999, though not as much as "Morphogenetic Sorrow".
* [[https://www.youtube.com/watch?v=Ius54l96xe0 Trepidation]] is the devil of the OST. It plays whenever you find a corpse, and it always goes along with extremely detailed descriptions of the bodies. Scary indeed.