There are the people you meet in lines or standing next to waiting for the show to start. I've enjoyed meeting all of them. There are a handful of people I've greeted at multiple shows, having recognized them from a prior show. Then there is the crowd response to the performance of the songs. There is an unspoken bond you have with the entire crowd and with the people standing around you and a unity that can be a really cool thing. There is nothing else like it. Incidentally, I like that the definition of acting "in concert" is to act together and with a common plan.
My summer concerts this year:
Dave Matthews Band, Comcast Theatre, Hartford, CT, 6-8
Wilco's Solid Sound Festival, Mass MoCA, North Adams, MA, 6-21 - 6-22
Cory Chisel, Cafe Nine, New Haven, CT, 6-30
Americanarama Festival with My Morning Jacket, Wilco, and Bob Dylan, Webster Bank Arena, Bridgeport, CT, 7-19