To do a level select enter the options screen and highlight the "Music Test" selection. Press Left or Right to select a level. Hold Select and press L, R, R, L, Start.
Hold L + R on controller two at the player selection screen. Player two may now select the same character as player one.
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.