From Bulbapedia, the community-driven Pokémon encyclopedia.
The Sky Jukebox (Japanese: そらのジュークボックス Sky Jukebox) is a feature in Pokémon Mystery Dungeon: Explorers of Sky that allows players to listen to any song from the game. It can be accessed in the opening menu and is unlocked after the player has completed the post-game Shaymin Village event. The Jukebox has 141 playable songs in total. When it is unlocked, not all of the songs will be available unless the player has completed the special episodes. One of the more useful features is the ability to use headphones and close the DS without interrupting the music, allowing it to function like an MP3 player.
Some dungeons, like Mystery Jungle or World Abyss, will not have their own song and will instead from other dungeons.
List of playable songs