Every night of the Kentucky All State Choir conference at about
11pm, everyone comes out to the balconies of the 18 story Hyatt
Louisville Hotel to sing the National Anthem. Here is one
performance from 2013.
Flat Spins in formation! Sound ON! Pay particular attention to how close they get to the ground in some of the maneuvers. Check this guy at 48 seconds into the video – almost on the ground and completely vertical. Amazing. Note that they stop vertically and then accelerate vertically.