The world knows of 44 songs that are featured on the The Beatles: Rock Band disc. The world does not know of the 45th. What could it be? It's a "surprise," non-spoiling MTV PR tells me.
The Beatles Rock Band will be released next week, which puts us in that pre-release timeframe during which secrets lurking in a game lurk no more. Now's about when we would find out that Raiden is actually the main character of The Beatles game. Or that the game is only six hours long and full of driving missions.
So we know what 44 of the 45 songs will be. A mystery remains.