the contestants go before a bunch of judges just to be able to get to stage 2,,they sing accopello and if the first set like them then they in front of a second set of judges and if they like that then they move to the next set,,,the 25,000 contestants are dwindled down to about 500 or so before going in front of simon and company...thats the way it was explained to me by a former contestant...
Unless they are a stand out (odd) then they get bumped to go before them. Like old guys singing about penises, cute little girls singing, etc.