Like my post from 1/3/10, this post is taken from some notes I have been making for an advice book for composers. In the previous entry I wrote about planning recital programs. Here are some very sketchy thoughts on concert etiquette - I would love more ideas if you have them!
Clothing
The typical “new music uniform” for performers is all black. No tuxedos, thank you. Formal dreses not required. Black dress shirt, black slacks, black socks, black shoes - for men and for women. Easy an comfortable. Now, there are no hard and fast rules about the style of said shirt, slacks, and shoes, and some groups dress more like rock stars than classical performers. I just wanted to tell you so that you have a default to fall back on. If you are not performing, but only appearing as the composer, you have even more flexibility.
Entering the stage
Enter quickly and with confidence. Stay in shape so you can move quickly. This also applies if you are sitting in the audience, not performing. I'm sure we've all had to sit through some slow-moving folks going to the stage, and we probably wondered why they didn't sit closer!
Bows
Don't forget to do this! Show your appreciation for the audience. Bow from the waist, like you're touching your toes. If bowing with other people, take the lead: make sure everyone is looking, then bow. They will follow.