Castlevania Chronicles Cheats

Hold L1 and R1 while selecting Original Mode, and you'll unlock an option to change the music played in the game. This works in Arrange mode, as well.

At the title screen do this (slightly modified for domestic release's button layout) classic Konami code:
Up, Up, Down, Down, Left, Right, Left, Right, Circle, X, Start.
Once done, a screen will come up showing ''Extra Option'' where there's a Date set and a Display Mode set.