UPDATE!!  I found a different video, which includes the whole song and more of an explanation!

After a little more research, I found out that the group is actually the Kentucky All State Choir and, according to the "About" section on this Youtube video, all the kids come out of their rooms at 11pm to sing the National Anthem.  Beautiful!!

When I saw this video, I was blown away!  High school students??  They must have been there for a chorus convention, because these kids are awesome!

According to the description on Youtube, the person who shot the video had checked into a hotel in Kentucky, which was also hosting hundreds of high school students.  It seems that many of the kids were causing a ruckus, until this happened:  18 floors of students, singing our National Anthem.

Apparently, it was in celebration of the opening of the Olympic Games.  Listen really well at the 1:02 mark!  This must be a trained choir of some sort, because they are awesome!

(Via Youtube)