So, as far as I can tell, there is no battle-mode/tug-of-war/etc in Rock Band 3. I was so confused at first and wondered if I was just a menu newbie and then actually confirmed my worst fears by double and triple checking some user posts by Google.
Can anyone point me to a thread that explains why this feature was dropped in between Rock Band 2 to Rock Band 3? My primary usage and best memories of RB1 and RB2 was having singing competitions with friends(not take turns, see who can get higher score) but singing together/vs each other. It's a memorable and awesome experience and made the game indirectly better than a lot of the pure "karaoke" games at the time like American Idol Karaoke Revolution, LIPS, etc.