Sound test
At the title screen, press Left, Circle, Down, Triangle, Right, Square, Up, X, L1, R2, L2, R1 + Start. Then, a "Sound Test" option will appear under "Option Mode".
Unlimited power spell
At the title screen, hold L1 + L2 + R1 + R2 and start a game. Then, a power spell charm with unlimited uses will be available as soon as the game begins.
View character biographies
Unlock all thirteen endings, then select "Pamphlet" mode. Now a new "Guide" option will allow data for each character to be displayed.