Specifically a certain tenor who makes a living off singing Nessun Dorma a third down. Very rude to the sound guys. NEVER be rude to the sound guys. Not sensible if you want to sound good.
This. Oh SO this.
It's so easy to strip out or overload a frequency and make a perfectly pleasant speaker or singer sound reedy or muddy. Killing off the upper partial harmonics will turn any voice or instrument into a pancake of uninspiring noise. "Forget" a filter, and the speaker's voice is broadcast to the nation with all its accompanying spit pops and lip smacks - and even a few which aren't actually really there at all.
Three people you never upset: the VAT inspector, the waiter, and the sound engineer.
Not that I would ever be caught doing such things, you understand.