Have you considered this? In order for the orchestra to use the photos in advertising and promotionally on their website, you should have a signed model release from each and every recognizable person in any image that's used. Personally, I'd want a signed property release from the venue, as well.
Now, the orchestra might already have on file a signed waiver from each participant, allowing usage of the individual's image to promote and market the orchestra. If so, at a very minimum I'd want to know exactly what that waiver says and, if it appears to be acceptable, would want copies of all of the signed waivers in my files, too.
Those waivers, if they exist, probably would not extend beyond orchestra-related usage of the images, I'm guessing. So, in other words, you probably could not use or sell the images for any commercial purposes beyond the orchestra's. That includes self-promotion usage, although you could display them in a portfolio (actual printed or virtual, which are not considered commercial usage as it stands right now), but that's about it.
I don't know what to suggest charging. The orchestra sounds as if it's a recognized charitable organization, in which case you might be able donate your services or only ask for a token amount for the shoot and/or usage of your images, get a signed letter from them acknowledging "fair market value" of your donation, over their charitable license number, and take a nice tax deduction this year. However, talk with your tax accountant about this.
I really don't think it hurts one's ability to charge reasonable fees for non-charitable work, if one occasionally "gives back" to worthy, charitable causes by donating services and limited usage of one's images. Ask for credits and perhaps a link from their website to yours, and offer reasonably priced prints to the members of the orchestra who might want a keepsake of the even themselves, especially playing in a major venue like Carnegie. Be sure to get not only broad shots of the orchestra as a group, but also some tighter shots of the individuals.
Is there a practice session, dress rehearsal? If so, that might be a time to get more shots than are possible during the actual performance.
There are sound deadening devices for cameras. They can be rented, if you have enough lead time. With an actual out-of-pocket expense like this, the orchestra might be willing to cover the cost. The same might be true of travel and lodging expenses.
It takes time to realize "good will" benefits that are established by helping out any charitable organization. A call back for a paying job can come months or years later, usually when you least expect it. Or it can happen the next day. It's purely speculative, but the more you get your name and work out for people to see, the more they will be inclined to think of you when they need to hire a photographer themselves, or to recommend you to others.
But, hey, I'm not an accountant or attorney.... Just a mere photographer.