I bang on about this regularly. It's a bigger problem than people think. Human psychology is such that nobody wants to lok a dick and be the only one singing in their block or stand. If a song is loud enough, there are loads who will join in to the songs which don't involve clapping. But because there are about 1000 singers in each singing section, it doesn't get loud enough to spread unless both are singing at once and it spreads both ways around the ground at once before the song is over.
I got laughed at on here once but some sort of acoustic/sound reflective solution which allows songs to be heard in both singing sections when one starts would have a bigger effect than people think.