Cops Pose as Punks on the Internet

How do you have an annoying live concert without anyone nearby calling the police though? Isn't it enough to break them up when they're in progress?

It's better to prevent a crime than to catch the culprits after it's committed.

By the time police show up - and especially by the time they're done breaking up the party - you have an entire neighborhood awake, babies crying, dogs barking, people will have lost 2 or more hours of sleep and who knows how long it would take them to settle down...
Obviously not as bad as murders or drug rings, but also not something you want happening regularly where you live.