A few of them.
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Probably my favorite of them all if I were forced to choose, a remix of this song was what got me interested in Zun's music/games in the first place. Yukari also ended up being my favorite character.
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A couple more favorites. These are from the 6th game, the first one for the Windows platform.
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This one is from the secret stage of the 5th game, you need an emulator to play the first 5 games.