How do you change the order/priority of connected controllers on the Xbox 360?

Title basically says it all. I play Rock Band with my family a lot, and I sometimes want to use the Guitar Hero III controller I have. It works fine, but it’s assigned a different port than my Rock Band guitar controller, even if the Rock Band controller is turned off. This has the effect of switching the order of drums vs. guitar onscreen, horizontally. I’m okay with it, but my sister can’t bear it. All I’d need to to is change the order, but I can’t figure out how.