Weeeell. I've been to many barbershop concerts. The fun part about barbershop concerts is that *everybody* gets to go "backstage" if they want. Most choruses will have an after concert party called an "afterglow" where the chorus, chorus quartets, and feature quartets sing a few more off-the-cuff numbers, and then if you want you can shmooze with the feature quartets (read: the "famous" ones. <G>) and try to sing with them, or get autographs or something. Fun.
As for actual more "commercial" singers/bands... well, I did go to a barbershop show with Rockapella as the featured singers. Ohhhh, that was sweet! I thought their tenor Scott was sexy before, but ooooooh can that guy *dance*! (drool) Unfortunately, the show was in Rhode Island, so we didn't get to attend the afterglow because we needed to make the long trek home. (Actually I can't even remember if they had one.)
Other than that, nada. Either there's just nobody performing in my neck of the woods, or I have no money for a ticket. Like right now, The Barenaked Ladies are performing at UMass in Amherst. But do I have any money to go? Nope. Blah.
Peace & Luv, Liz