Your music doesn’t have to be an original composition. But it does need to be conservatory level. If it’s not, don’t bother sending it. My kid is an oboe player and lets just say…she didn’t compose her own music…but she was top ranked in our state, and played quite well.
No karaoke…just no. I would not suggest a popular piece of music either. It’s just not going to improve your application to sing a Disney song…at all…or any other movie theme song.