If I plan on seeing a concert here, do I also have to be 21 even though I will only be there for the music?

Some shows are all ages. It depends on the show.

Yes

I think so

I have been there many times and never seen a wristband. Might depend on the band.

Yes, best deal is to contact them directly but if I remember correctly, the shows I attended drinkers were ID'd and given a wristband to purchase drinks, underage got no wristband.

Call and ask

Your best deal should be to contact them directly