You don't need to learn a new song for every audition! Build an audition binder ahead of time so that you are ready anytime with songs you feel comfortable with.
You should include:
A Contemporary Ballad
A Contemporary Up-Tempo song
A Golden- Age or Standard Broadway Ballad
A Golden-Age or Standard Broadway Up-Tempo song
Bonus! Have another song that shows a special skill. This could be amazing diction, comedic timing or a screaming rock belt!