Yep, there's a glitch in the PS2 version of GHIII where you play on Expert and Lou plays on Easy. It does nothing favorable for the player, and only makes the song even harder. Anyways, Here's (http://www.youtube.com/watch?v=FpbwUS3xbvc) the video I made showing the glitch. Everything you need to know about the how to do the glitch is in the video and the description.
I'm not sure about the 360, PS3, and Wii versions having this one though. Enjoy.
That's pretty cool!
That happened to me when battling Morello once. xD