Some of you may not know it, but you can unlock the soundtrack of the Nintendo DS installments in Pokémon Brilliant Diamond and Shining Pearl. To do this, you just have to follow the following steps:
- After completing the Pokémon League, return to the Great Lake Hotel.
- There, you will find a house with a pool in front. It’s the only one that has it, so it’s easy to find.
- Inside you’ll find characters who pay tribute to the game’s developers (including Junichi Masuda).
- By talking to the character holding the guitar, you will unlock the key item.
With this item in your possession, you can activate the soundtrack of Pokémon Diamond and Pearl for Nintendo DS in the game just by activating it from your bag.