it really depends on the directors i think. at my school they usually want to see songs from the show. but like i said, it's best to know what the director wants.
Generally speaking, unless an audition notice says to sing from the show, it's best to choose a song from another show that is "in the style of the show." That said, go prepared with a song or two from the show in your book, in case the director requests to hear you sing something from the show. Usually that happens in a callback, but it can happen in a first audition, depending on the director.
Yes, what everyone else said. However, if you're auditioning for a show and are going for a particular role (and can only feasibly play that role), it might actually be a good idea to sing from the show. For example, let's say I have an audition for Into The Woods. At my age and type, Jack is the only role I could feasibly play, so I would audition with "Giants in the Sky."
Well I have a Seussical audition coming. I have played Horton. I use the first part of Alone in the Universe for all my auditions. It does not specify to use songs from the show. I want Horton again Should I use it?
It is HIGHLY recommended not to, but with the venues you're auditioning for you should be alright. Just make sure you can rock it, not be mediocre, because there are probably going to be a lot of bobos poorly singing those songs.
HSM- it looks like someone took a shit on Footloose.