is there seating?

Not really, very few seats in balcony. Main floor is standing only.

Generally speaking, Concord Music Hall is a standing room venue. There are a few benches in the elevated portions in the back of the room and the balconies.

I have been there a few times and never seen seating. Expect to be standing the entire time -- for the ladies, I recommend NOT to wear heels because you will be sorry once your feet are dying. You also can't lean against the walls to rest -- I've known people (including men) who go to the bathroom to sit on the toilet to rest their feet during shows at this place.

Don't go if you are unable to stand for long periods. I stood for almost 2 hours and it didn't help with my arthritic knees.

Expect to stand through the whole show. If there are seats, ive never seen them or used them. If they exist they are in very short supply.

Yes