What is the Gameboy
A hidden device in game called the Gameboy Player allows you to change the game's music to Gold and Silvers music for a more nostalgic feeling.
where do i find the Gameboy
Enter the Celadon Condominiums next to the Pokemon Center in Celadon City. Use the elevator to get to the third floor. When you exit, your friend will tell you about the Gameboy Sounds. Talk to the man next to the globe after collecting all of the Kanto badges to get the Gameboy Sounds Device.