Rock Band Help

[Nightwing]

Ok so for Christmas I recieved this wonderfully addictive game along with the full get up of drums,guitar and mic and I love it.

Ive been hammering away with the drums today to find I unlocked an achievement for unlocking a 'Theater'

Can anyone tell me what this is and how I use it?Ive searched through every menu and even read the instruction book cover to cover and can't find anything about Theater mode or anything even related..

Has anyone got a clue what this is and how it works?

 

[Joker]

The venus in solo are named different things. Big Venue, Arena, and...Theater.

 

[Nightwing]

ah it did say I unlocked poison in theater but i thought today it might be a venue...wasnt sure...

cheers though