Encountering Champion Blue outside of his room in Indigo Plateau's Pokémon League enables the player to make music play where it isn't supposed to.
This applies to Champion Blue encountered through the old man trick (via a '/' as the 3rd, 5th, 7th, 9th or 11th character) or Ditto trick (via a Special stat of 243).
Set up
Encounter Champion Blue with the old man trick or Ditto trick then win. This causes the victory music to keep playing outside of battle. The sound bank values (memory addresses C0EF, C0F0) remain at 08 (in battle), meaning that bumping into a wall causes the wrong sound effects to play.Tricks
Set up the glitch in a place with grass or water tiles, and then battle a wild Pokémon. After running, the wild Pokémon battle music will stay out of battle. Defeating the wild Pokémon causes the wild Pokémon victory music to play outside of battle. Set up the glitch in a place with a Trainer. Defeating the Trainer causes the Trainer victory music to play out of battle. Black out, either in battle or out of battle, and the previous location music will play in the location you appear after the black out. Warps will not update the music, but map connections will. Saving and resetting will not fix the glitch. The title screen music can be played in game simply by choosing 'continue'.Fixing the glitch
There are two permanent fixes, and a temporary fix in Pokémon YellowPermanent fixes: Beat the Elite Four and Blue in the Indigo Plateau Start a new game
Temporary fix (Pokémon Yellow exclusive): selecting 'PRNT' in the Pokédex will make the intended music play, but the music still sticks when using warps.