My band played a wedding. many years ago. A friend of the bride, was a club singer in Vegas, she was fabulous, and we got a real time lesson in putting on a show. I'd never worked with a "real" singer before. So when she called Johnny B Goode, in F#, I was real happy, I'd focused on not being key dependent. The guitar player on the hand was earning his money (no capo, no time for a capo).