Attending the symphony is an experience many people never get, so you don’t want to ruin it by showing up in the wrong attire. The symphony is a classy place to be, and dressing accordingly is part of it.
Firstly, take into consideration what night you’re going, and for what reason. Opening night will see quite a few tuxes and ball gowns, so don’t be the only one in a sport coat. Benefits and charity performances also carry with them a more formal dress code. If you’re going with your boss (or to impress a colleague that’ll be there), dress up rather than down. For men, a tie can’t hurt, and make sure your dress shoes are shined. Make sure your tux isn’t wrinkled, and make sure it’s not flooding to show your white socks (better yet, don’t wear white socks). Women should focus on a dress, nice heels (no need for stilettos, just something to compliment the dress), a small purse, and a prim appearance. Lipstick and jewelry are two simple things that can boost the sophistication of your appearance if you’re not into a full-on transformation for the night. Word of advice- don’t layer on the cologne or perfume; there will be many people within a very small radius around you, and someone may be allergic to or distracted by the scent.
Those instructions can apply to any performance, but don’t have to. If you’re seeing a non-business related show, you can think classy comfort. Men should still wear their polished dress shoes and nice slacks. A sweater or button-down shirt under a sport coat will suffice, as will a simple hair style.
Women have more of a responsibility with their appearance, but also have more varieties. A semi-formal dress is perfect, but a nice summer dress or blouse and skirt will suffice. Nylons and shoe choice are up to you, but no tube socks or running shoes. Makeup and a nice hairstyle aren’t required, but you want to look as well-kept as the people around you. Having your hair up and out of your face is most convenient for a long performance, and will also flatter your appearance more than leaving your hair down.
Children can get away with their Sunday best, but make sure pants are pressed and dresses are ironed. The other symphony-goers will be sympathetic of a few wrinkles by the time you get there, but if you start with a clean slate, you have a better shot of keeping the kids looking fresh.