You may have heard this before, but it bears repeating – practice in your audition outfit and shoes. Too tight/too high shoes, a jacket that restricts your bow arm, a dress that keeps slipping – these are distractions that you don’t need when you are in the audition room! And don’t just try everything on – play in the outfit. What feels good walking around isn’t necessarily comfortable to perform in. It’s surprising how much we can tolerate something uncomfortable, such as a restrictive shirt or high heels, in our daily life. I remember a singer who wore a beautiful dress and high heels to an audition – she walked into the audition room, stood there for a second, and then asked the faculty if she could take off her shoes to sing. She said that she could feel that the heels were that little bit too high, and her pelvis was tilting to compensate and affecting her support. I applaud her for recognizing that fact, and having the courage to simply do what she needed to do to sing well. But – she should have tried to sing in those shoes before the audition!
On a secondary topic – what exactly are suitable audition clothes? Besides being comfortable (see above!), I would simply recommend nice attire. Concert dress is fine, but not necessary. For men, a nice shirt and slacks is fine – a suit and tie is not necessary. For women, a simple dress, blouse and skirt/slacks is suitable – a performance gown is not necessary. Basically, look like you made an effort to look good!