I've seen this video clip several times, and every time it takes my breath away.
In my opinion, everything about this is perfect. The heavenly voices = perfect. The looks of confusion, astonishment and then pure wonder on the faces of the people that are there and who slowly realize what's going on = perfect. The sheer awesomeness that humans possess to come together and create something good = perfect.
While I would have loved to be a part of this magical moment, it's probably a good thing I wasn't there because I wouldn't have been able to stop myself from standing up and singing along. If that had happened, in the midst of these beautiful voices, you would have heard a noise that sounded like a trapped mouse. And.... that would've been me.