Well, if I have to pick individual games, it would be games from two franchises, so I'll go by franchise.
<spoiler=5. Beyond Good and Evil>Christopher Heral outdid himself here. The game covers a huge range of emotion, and his music covers that range beautifully. Whether it's a grimy club song with a ridiculously catchy hook:
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...to intense chase sequences with speed percussion and driving rhythms accompanying:
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...to brilliantly simple and pleasant moments of rest:
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...to complete balls-out WTFery:
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...Beyond Good And Evil's soundtrack has you covered.
Man, I love Slaughterhouse Scramble. I don't even know why.
<spoiler=4. Myst - Robyn Miller and Tim Larkin>I've mentioned my unending love for Myst before. One of the many, MANY reasons for my love, as well as the games' place in the hall of gaming classics, is the utterly surreal and oboe-driven music of the first two games.
Robyn Miller is to blame.
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Violins and oboe, swapping with timpani and string section? Madness! Then in come the harps and harmonies, people, this is written in MIDI. MIDI, DAMMIT!
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In Riven, Miller branched into more tribal sounds, to add to the air of the game (which centers on a rapidly collapsing primitive-ish civilization). The results are bloody spectacular.
Plus, he bloody knew how to set up the entrance of the villain.
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I would feel guilty if I didn't include the work of Tim Larkin, too, who did Uru and Myst V. Unlike Miller, he went for significantly more ambient themes, which had less musical patterns and recognizable rhythms to distract you from the area you were exploring.
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Delightful. He fully understood what he was writing for, and showed mastery of his instruments, even though he didn't have a real orchestra to work with (tragically).
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Also worth mentioning is that he shared Miller's affinity for melancholy oboe, so there's that.
<spoiler=3. Tropico>I don't speak Spanish very well... at all. That doesn't stop me from adoring the Caribbean flavor that added so much personality to the first, third and fourth Tropico games.
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Tell me you aren't tapping a foot or bobbing your head to that. TELL ME.
The happy and rhythmic tracks really contributed to the inherent surreality of the series: You're ruling an island with an iron fist, squelching rebellion, throwing the election, and many other classic dictator-ish things, and yet the game maintains a bouncy and pleasant look, playstyle and sound.
VERY bouncy and pleasant sound.
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I swear I stop the game every damn time that song comes on. Every. Time.
It's all just so... catchy and happy. A rarity in games in the first place, it's especially rare for it to be done so well.
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The only reason this doesn't come in higher is because there's only 15 tracks or so per game, which play on infinite loop.
(NOTE: Tropico 2 was about pirates instead of dictatorships, and had significantly less awesome music. I don't know why.)
<spoiler=2. Silent Hill>No words needed, we've all heard "Room of Angel" and have experienced the surreal sadness that Akira Yamaoka has no difficulty instilling.
So have it again.
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But wait, you say. That's just his vocalized tracks for particularly poignant cutscenes! What of his ambient in-game stuff? Are THEY any good?
The answer is yes.
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The chills won't go away!
He's definitely not all bombast, either. He manages to draw chills and tension from comparatively quiet accompaniments, as well.
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Repetition is the key to holding up a good atmosphere, a key that Akira knows well and wields well.
But not all the Silent Hill music is subtle(ish) and designed to draw chills through sadness and feelings of fear. Sometimes, it wants nothing more than to scare you so hard your pants turn brown.
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Sweet dreams.
<spoiler=1. Myst - Jack Wall>Hey, you say, you already included Myst! CHEATER!
Hear me out on this one, and understand why I put Jack Wall's work on Myst on a different plain than Miller or Larkin.
More specifically, listen to these twenty seconds.
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The defense rests.
Jack Wall did a positively PHENOMENAL job on the Myst series. Not only did he get an actual orchestra, he upped the dynamics and scope on everything, while still maintaining a "Mystlike" feel.
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Richer bass, rhythmic sectionals, ridiculously ambient focus, and throwbacks to the original score, this soundtrack has it all.
All of it.
Much of the stuff he wrote for Myst was significantly more intense than what Miller or Larkin put out, partly because of the live orchestra, but holy cow, does it ever contribute to the game's atmosphere. Myst III and IV felt more frantic and dangerous than any of the games ever felt. Many will (correctly) claim that this is because Myst is not meant to be frantic, but it made III and IV hook you all the harder when their themes coursed through your ears.
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Let's also not forget the fact that Myst III had Brad freaking Dourif play the bad guy. So Jack Wall also had the honor of writing the music that Brad Dourif got to have a massive breakdown to.
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I rest my case, this soundtrack is a work of damned art.