You could always do “concert black” since you are the musician:

If you are female, you could do either a pair of nice black dress pants or a black skirt with a dressy black blouse or top. (If you don’t have a nice black top, you could choose another color.)

If you are male, a pair of black dress pants with a button down shirt and tie would be good.. maybe black shirt with a silver/grey tie if you already own that… otherwise another colored shirt/tie would do just fine as well!