This is a video from the first MLS home game for the Portland Timbers. They rebuilt the stadium to make it soccer specific, instead of multi use with the Portland Beavers.
They decided to sing the national anthem, as a whole. 20,000+ people singing at the same time. I watched this on ESPN when it was going. The thing is, I had headphones in studying. I watched it, but missed the song. The whole game though, the crowd went wild for the 3 goals I saw, and after each, the official mascot of the Timbers(Timber Joey) would use a chainsaw and cut a piece of a tree off.