I am a Marine and extremely proud of what I have been able to accomplish during my time in and out of the service. It wasn't easy and not everyone makes it to the end to earn the title of United States Marine. I know a few people that are Marines and they came in through the Marine Corps Band. This is a very elite group of Marines and this sounds like it may be a perfect fit for your end goals. Talk to a recruiter and see where it takes you. Good Luck and Semper Fi!
You have a LONG time before you need to figure out what to do. Who knows? When you're 18 you might want to be a fashion designer or something lol. I do share your love of music though and it is a great experience making songs (: