I'm not sure what all the details are... but I'm sure it has alot to do with contractual obligations.
The first contract I'm sure has to do with what ever the full deal was with "Baby-Ruth" Candy Bars and MLB due to "Baby-Ruth" being the sponsor of the contest. Loop-holes were everywhere in that contract I'm sure... and reading into the winning prize tells all.
Per the
MLB/Baby Ruth Contest Website.
GRAND PRIZE (1)
Sing "Take Me Out to the Ballgame" and you could
win the opportunity to lead the singing of it during the 7th inning stretch of the 2008 MLB All-Star Game at Yankee Stadium.
FINALISTS (3)
Finalists receive a trip to the 2008 MLB All-Star Week ™ for themselves and one guest. Trip includes transportation to the MLB® All Star Weekend in New York, 2 tickets to the 2008 MLB All Star Game, and ground transportation to/from hotel/airport and 4 days/3 nights hotel accommodations.
FIRST PRIZE (7)
First Prize winners will each receive one 2008 MLB All-Star Week ™ Gift Bag and one year supply of BABY RUTH ® product.
Notice that it does not say anything about using instruments (allowing or disallowing, so they can interpret the way they want) - the only thing in writing was that they were allowed to lead in the SINGING of the 7th Inning Stretch.
BTW - I would have assumed that since the uke and tuba were in the video, they SHOULD be in the performance (like the video that we all voted for), but MLB, Baby Ruth and the Stadium Organ Player probably saw differently.