Musicianship is absolutely worth including and would certainly be looked on favorably - more so if you are highly accomplished. It's not a terribly unique attribute unless you have achieved some incredible success, but it's absolutely worth mentioning and even featuring.
As a professional musician now turned physician myself I can say without a doubt that my musical background was phenomenal preparation for medical training. Any idiot can memorize amino acids or push electrons around a stick drawing, but walking into an angry patient's room filled with fuming family members and walking out to hugs and thank you a takes something else: it takes art.
It's that undefinable yet immediately recognizable essence. I think musical accomplishment sets you up to find that. Just like your first foreign language is the hardest, so is your first art. Once you've already been down that road, it's much easier the second time.
As someone who's learned multiple instruments, you have a deep understanding of this. You understand the value of playing scales and etudes for years even if they aren't what you will ultimately "use" as a performer. You've spent hundreds of hours perfecting tiny details of a piece, any one of which nobody will ever notice, but put together transform music into art. You understand what it means to truly learn something beyond simply cramming it for a test (can't cram a concerto!). You have learned that fine balance of developing your own perspectives on a piece while still being able to yield parts of your vision to the overall vision of the conductor or director. You've learned how to collaborate with others, both in large groups and small and learned the intricacies of negotiating each - the ability to contribute yet blend in an orchestra or choir; the ability to play or sing as a true soloist yet collaborator in chamber music. All of these hone skills that you will use every day in medicine.
Perhaps most importantly, you've been learning how to listen. Truly listen. This is what will ultimately become your secret weapon. Such a vital skill but is never really taught. I think people confuse hearing with listening and just assume people can do it, but it's obviously so much more involved than that. Music (and acting actually) gives you unparalleled training in being able to listen so intently that you're actually saying something. Great music making is 90% listening and only 10% technical skill; I think the numbers in medicine are probably not far off of that.
So yes, talk about your music. It's easy to relate it to medicine and incorporate it into an argument for why you will succeed.