I have been singing in choir for 7 years by now, mostly in school and student choirs during study years (I have no professional training whatsoever). Now I applied for a better choir in our city (composed mostly of professionals, but they take talented amateurs too); they will have audition in 3 weeks' time, and I've been told to bring a song which I would like to sing in front of the others (besides the audition led by the choirmaster).
What are they looking for/trying to hear at such auditions? So far I've been singing in Soprano, but I am more a Mezzo-soprano. What song would be suitable to show what I am really able of? The genre of the song can be literally anything (from folk through jazz to pop, anything).