Let's be practical. I have given this advice many times before and expect to do so for a long time to come.
Pick the song that is easiest to sight read unless you are taking your own well-rehearsed accompanist.
Many an audition has run aground on the shoals because the pianist couldn't play it.
The big one was in the 70s when so many young women sang The Miller's Son and so many accompanists did not learn it. Not pretty.
Hair may be a rock score, but many of the longer songs have a traditional structure and also require real voices. Find a rock song where the original singer had a legit instrument. Somebody To Love/Grace Slick is a real good example.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher