I witnessed a girl of around 18 being shouted at, very publicly, by a much older man for singing more loudly along to her friend's song (to which she obviously knew the words) than the song sung by someone else immediately before.

Thanks for the explanation. I was a few feet away and thought the guy was just nuts. I guess if he'd been the same age as the people he was shouting abuse at, he'd have been rapidly shouldered out the door and left to cool off in the street.

Those young singers were really powerful. I haven't heard a large group of people that age singing like that in Britain before. Where are they from?