MizMoya,
Don't feel pressure about the phone call. Just be polite, introduce yourself, say you are interested in auditioning for the program and ask to set up an audition time with them (and possibly campus tour/ tour of the facilities or something if you are interested). Make sure you have a calendar in front of you in case the date/time you were planning on isn't available- that way you can easily tell them what other days you can do it. Also, if you haven't applied to the University yet, get that done asap because they will probably ask if you've done that yet- so that way you can tell them it's already under control! All of the faculty are very nice, and remember they want you to do well!! (Just as much as you do
Obviously the phone call has nothing to do with their decision to accept you, so just be polite and professional and it'll be no big deal!