I’m under the impression that when one submits supplementary material, the admissions committee, which of course is not expert in all fields, will pass the supplement on to the relevant faculty for them to evaluate it. Your art portfolio? Going to the fine arts or graphic design faculty. Your classical instrumental performance? Going to the faculty member who teaches that instrument, if they have one, and otherwise to the conductor of their orchestra. I have no idea what they do with vocal performance if they don’t have a vocal performance teacher.
If you have a teacher, ask them for guidance on your choice of music. If you don’t have a teacher, perhaps you should consult with someone at your local conservatory, if there is one near you.