Clapping on the on-beat sounds weird and wrong on (most?) songs. In (most?) 4/4 songs, that means clapping on the 1 and 3 sounds bad and 2 and 4 sounds good/normal.
But an audience of a bunch of random folks just getting excited can get it wrong!
This video of Harry Connick Jr. extending a bar just one extra beat to adjust the audience to clapping on the correct beat is extremely friggin cool.
(via Alan Smith)
