I don't mean to rain on anyone's parade, but you may want to take note of section 7.7.6 of the manual, which states, "Please do not add music to your cart." I think this rule is new for this year. It's a bit disappointing to me, too, because I really liked having music on our cart to keep us upbeat on the loooong walk to the Dome last year.
Manual - Section 7 (PDF warning)