While I haven't been in the Mass Mutual Center since their remodel 5-6 years ago, I can tell you that the lighting is (or at least, was) predominently some kind of mercury vapor lighting. At least, that's what they used for hockey games. They may have since gone to some kind of lower cost to operate lights such as sodium vapor or even LED. For a concert, however, expect spot lights and various colored lighting as well. In short, the white balance will be a real nightmare to deal with...especially if trying to go unnoticed and not use a flash.
Assuming the removable lens rules are being followed (a phone call to the MM Center should provide all the answers), I'd probably go with a 15X point and shoot camera that can shoot in RAW. Shooting in RAW gives the most lattitude during post processing to do whatever color correcting is necessary to 'get it right'. Shooting only in JPG is quite likely to be a problem due to various kinds of mixed lighting.
Off topic...don't park in the multi-level parking structure across the street. It'll take close to an hour to get out of there when it's done as they frequently have only 1 lane open for exit. Nice of them, huh? Walk the extra block north and park in the 'flat' parking lot. You can get out of there quite easily as a result. If you'd rather have free parking at your own risk, Bliss St between Main and East Columbus has an unstaffed lot at that hour. The lots on State St near the courthouse may or may not still be staffed at that hour, I can't say for sure.