In PV Mode (Rhythm Game Mode)

Secret Commands:
By selecting a song with the triangle button to watch a PV, wait for the loading screen.
When the title appears (the screen where you have to push circle again to start the PV) hold these buttons to watch a modified PV:

R1 = PV playing as Off Vocal / Karaoke Version
L1+Up = PV playing without background in a Blue Box.
L1+Left = PV playing without background in a Yellow Box.
L1+Right = PV playing without background in a Green Box.
L1+Down = PV playing without background in a Red Box.

Normal Commands:
X = Toggle Lyrics On/Off
Square = Toggle Repeat On/Off
Circle = Play/Pause PV
Left D-Pad = Restart PV

In Live Concert Mode

Commands:
X = Toggle Lyrics On/Off
Square = Toggle Repeat Off/On
Circle = Play/Pause PV
Left D-Pad = Restart PV
Right D-Pad = Skip PV
Left Analog Stick = Rotate Camera
Right Analog Stick = Pan Camera
L1 or R1 = Switch Camera Angles
L3 (Press Left Stick) = Reset Camera Rotation
R3 (Press Right Stick) = Center Camera