The biggest?
It depends on what constitutes a "Choral competition".
Indiana University has IU Sing which is a competition that involves singing, dancing and some acting.
Houses start preparing for IU Sing in late September of the first semester and the entire things culminates on a weekend in Mid to Late February!
Pretty much all of the greek houses get invovled with IU Sing (and there are 40+) and winning it is a pretty big deal.
The competition also draws a large crowd. The auditorium usually sells a few thousand tickets for the event!
Its also a pretty big social event since houses usually "pair" for it. That weekend is filled with parties.
If you want more info, go to
http://www.iusf.bloomington.com and click on the link for IU Sing.
Its a HUGE event.
XP2k