How do you change port of wireless controller on XBOX 360

My friend just got an XBOX 360 and rock band. He wanted to play bass with the controller, since his brother was using his only guitar. But the problem is when the wireless controller connects, it goes to port 3, but to use it for bass, it needs to be in port 4. How do I change this?How do you change port of wireless controller on XBOX 360
unplug all the cords and the hard drive.



then



connect 3 controllers THEN connect the bass



then you can turn off the other 3.



The question doesnt make much sense but thats all i can think of