It'll depend mainly on your interviewer(s) and how you put forth why you play the instruments (include what you have learned from it and what additional experience you got).
Here's a true example of something very different from most medical school applicants:
I heard once from a professor at JHU talk about one of their medical students' experience. He said that his gpa wasn't competitive with the usual average, but he received an interview from JHU. One of the questions asked by the interviewer was, "Why do you have a lower gpa?" The student told him that he works at a nightclub and go to school simultaneously, so he didn't have enough time to study. However, he says that by being at the nightclub, he not only met all kind of people and enhance his interpersonal relationships with co-workers and customers, but also became a wine professional.
After hearing that he knows a lot about wine, the interviewer pulled out a bottle of wine and poured a glass of wine for the guy. He took a sip, thought for a little while, and told the interviewer what approx. year the wine is, the history that goes along with it, where it came from and other detailed information. The interviewer was impressed by his knowledge and asked if he wanted to go out and sample some more wine later on. And THAT'S the story of how that guy got in JHU medical school!
If you can make an impressive story as the above, it might just get you in.

Good luck!