If you are SNEAKING a camera into a concert, that means cameras are not allowed.
I've seen people arrested and thrown out of the venue for attempting to take photos where signs prohibiting cameras, including cell phones with camera are prominently displayed.
Oh, please! I used to sneak tape decks into concerts and when the Grateful Dead finally allowed tapers to set up microphone stands and record all they wanted... ticket sales exploded. They couldn’t find arenas big enough, even on a tour schedule.
The DON’T rule is:
DONT FIRE A FLASH IN AN INDOOR CONCERT!
Sneaky people lack integrity.
I bet to disagree with your inappropriate attack on my moral character:
“Integrity:

the quality of being honest and having strong moral principles; moral uprightness.”
Sneaking a camera into a concert is not dishonest. In order to be dishonest, I would need to first promise that I was not bringing a camera into the concert. So no dishonesty exists, except, perhaps, with the morally dishonest “shrink wrap” agreement of ticket holder terms.
Sneaking a camera into a concert is not an immoral act. In fact, musicians I know WANT me to photograph their shows.
Concert promoters create all sorts of stupid, senseless and unfair rules. Performers at Coachella can’t play shows within 1,000 miles of the festival for six months.
I’m a photographer. I shoot. I don’t ask trees, shrubs, mountains or rock stars for permission and I sure don’t need you faux morality in my life.