I'm not sure if this is a bug or design choice but after Alphinaud finish calling the Linkshell, the 'intense' background music keep playing after the cutscene by no short amount. It become the new permanent BGM of Labyrinthos area.
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Now I know according to the story you are in a rush to get the ark off the ground but isn't using this music for the rest of the game is overkilling it?
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I know I can turn off BGM audio but I don't want to miss listening to the music during side quests, not to mention I really like the original music of this area, the night version was very relaxing to listen to.