If it’s a club with low lighting: black shirt with collar & short sleeves, or black t-shirt, jeans.
If it’s an outdoor stage event with open lighting: Any t-shirt, jeans. If it’s over 85˚ I wear shorts.
If it’s a church gig: light-toned shirt with collar, jeans.
Back in the day (c.1972), the band I was in auditioned for Disneyland. I was 17, everyone else was 22+. I wore short hair (‘cuz it’s easier when surfing) and the other four guys had very long hair. The Disney guys loved our audition tape and asked us to come up and check out the venue he had in mind for us. The stage was the one that came up out of the ground (I forget its name) and as the band came up out of the ground (playing a current pop hit) they were all wearing bright red jumpsuits with white trim, and shiny black shoes. They were killing it, too. Really tight, great singing, lotsa showmanship, but those jumpsuits were a dealbreaker. Then our lead guitarist point out the other issue: everyone had short hair, coiffed like Donny Osmond. We declined any further auditions.