Howdy,
That is a way cool choral performance! I've never seen or heard a group that large doing vocals like that.
There's a group named "Take 6" that is all acapella, and they do all of their instrument sounds and other effects with their voices also. It's not as big a group (there are only 6 of them), but you should hear some of their music - fantastic! You can hear some clips at
http://www.mp3.com/take-6/artists/2031/songs.html
ttfn,
Sherry