Enter the option screen and highlight the "Music Test"
selection. Press Left or Right to select a level.
Hold Select and press L, R(2), L,
Start. Note: This also works for the Boss levels.
Very hard difficulty level:
Wait until the "Press Start" text flashes four times
at the title screen, then hold R + L and press Start.
Select the "Very Hard" selection from the option screen.
Same character match:
Hold L + R on controller two at the player selection
screen. Player two may now select the same character as player