Altered Beast Codes:

Hidden Options Menu:
     Hold X and press the Start button at title screen

Continue Game on last stage:
     Hold Square and press the Start button repeatively after death

Stage Select:
     Enable  Options  Menu.  Choose a stage, hold square and press the
Start button

Choose Beats for each stage:
     Hold Square, X, Circle, Down/Left and Start at the Title Screen

Sound Test:
     Hold Square, Circle, Up/Right and Start at the Title Screen