I'm at the Poly now, and saw the MK Hallo-Wishes from the Poly beach. I can confirm that they did NOT pipe in the music. I don't know if it would be any different for the regular Wishes or not. It seems to me that a couple of years ago I watched Wishes from the Poly beach, and they did pipe in the music, but it wasn't very loud at all.
I was there 3 weeks ago and they do pipe it in but it is EXTREMELY hard to hear. You have to be sitting next to the speakers on the walk ways to hear it and usually that means an obstructed view.