I think you have to compare what they do at "real" air shows these days.
At Reno last year the Air Force demo team (Thunderbirds) called out manuvers and had some good music during the show. I think this is very appropriate to and RC show if done correctly. Other than that they didn't have any music, but did anounce what was coming up next and gave updates on race leaders and stuff. I think the F22 also had some music playing during it's demo, but I couldn't hear anything since it was so loud
It sure would take away from the atmosphere of the show if music was playing during the fly-byes of the planes. It's so great to heard those motors going bye.
Jeff