The "tune up" cacophony at the beginning. The now-too-often 5 minute standing ovations that are 99% of the time not deserved.
Don't get me wrong, I love the occasional classical concert.
The only way I can be persuaded to go to ANY level of that occasion known as “concert” (or recital or play or...) is to allow me to first consume at least three stiff shots of scotch, be transported so as to arrive no more than three minutes before the festivities begin and then to allow me to sit through the thing with my eyes closed and absolutely no interruptions of any kind.
I absolutely LOVE good classical music, but I have no patience at all for the usual Music Snobs that intrude themselves on its performance.