Performers dress to reflect an ideal that is aspirational, alluring, shocking, representative, memorable.
Performers are remembered for their costumes i.e. Ziggy Stardust, Amanda Palmer's underwear, Jimi Hendrix.
Costumes usually reference a historic trend or a story i.e. Mikelangelo a surf western musician dresses and acts like Elvis, Alice Cottee a sultry singer styles herself like a 1940s cabaret singer, Fun Machine wear spandex and sequins like kids at a fun party.
These same performers shop at vintage clothing stores like April's Caravan to find looks that create the image of the stage persona.
Costumes don't necessarily have to function although they must permit the wearer to perform.
Sometimes the references are focussed single sources rather an combination of elements that create an idea i.e. Daft Punk who create electronic music dress in 'futuristic' costumes that are based on our interpretation now of the future.
"Science fiction isn't about the future, rather its about the day it is written in." William Gibson
Stories can engage an audience that is not attracted to 'fashion' e.g. comics, movie characters.