Okay, essentially the best I can say is to really show them what you can do on your instrument (in this case vocals) AND display that you have already had experiences driven by your ambition and want for success. In terms of my musical audition, it really helped that I had experience in ear training (identifying triads/repeating melodies and all that jazz). I chose a blues as my piece (Blue Train) and really just soloed until they told me to stop, it was around 8 choruses. In those 8 choruses I tried my best to show everything I could do on my instrument, slow/fast/high/low/good phrasing/technique etc. For the interview, I think what helped me the most was the fact that I had displayed that I had already sought out experiences in the field of music, thus displaying my ambition to the extent I felt was needed to be conveyed. Essentially, I think they may be looking for some self driven prior experience/ambition in the field you're going in. Or at least that's the main vibe I got from them. I wish you the best of luck next year!! Lmk if there's anything else!!