I'm gonna go in the opposite direction of Johnny and say have this conversation with your boss now. You're going back to school and you're moving locations, so there's definitely no chance of you staying. You're also not leaving for reasons that could be deemed negative against the company (don't like coworkers or boss, going to work for a competing firm) - you're leaving to pursue a degree that sounds like it has nothing to do with what you're currently doing.
While Johnny's right - you don't owe the company anything - that attitude doesn't do well if there are bridges you don't want to burn. You say you're a high earner and you'll be difficult to replace - good for you! Sit your boss down now and say that while you enjoy working here and what you do, you're following your passion and will be returning to school in May. You'll be happy to continue working hard until then, but you're very excited for the new opportunities you'll have in the music industries. You've really enjoyed working with him/her and your team, and you'll miss them. While you're happy to keep up your pace, you really want to take X amount of days off sometime in March to visit so-and-so before you start devoting your life to studying again. Or, you want your last day to be April 30th, but you have X days of POT left, so what should you do about those?
This is assuming you have at least a semi-positive relationship with your work (if not, screw them). But if you open the conversation now and let your boss feel like you're reaching the conclusion together (you're leaving either way, but it'll make him/her feel better), you'll be able to leave with good recommendations and references, a positive ending and maybe (but hopefully you'll never need it) a job if life in the music industry doesn't work out.
(Why, yes, I did win brown-noser-of-the-year award, why do you ask?)