[Followup to #6]
I will have to concur with what everyone else has said so far.
I was once in a position very similar to yours. During my high school years I decided I really wanted to go straight to Japan and stay for good. I thought it was bad enough that I had to stay put to finish high school, why should I want to stay for another four or more years on top of that before I could make the jump?
I spent a lot of time thinking of how to get straight into school in Japan, but ultimately it didn't work, mainly because of the lack of funding options at the time.
I started school in the US, and during my first term I very quickly re-thought what I wanted to do with myself and underwent a bit of an attitude adjustment, to come to the conclusion that I should strive for a career that I find suitable and satisfying, rather than getting so caught up on where I wanted to be.
It paid off in the end, as I came out with a better undergrad education than I might have if my previous attempts for Japan had worked out. I still got to spend a year in Japan, which I found to be quite enough for the time being, not to mention that it was infinitely easier to fund.
Also, I think spending just a year on a study abroad is a good way to see whether or not you really want to stay any longer. I got pretty burned out after a year in Tokyo, and was really ready to go back to the US for a while and get back on track academically.
I did wind up coming back to Japan after graduation, and things have worked out much better than if I had been able to go through with the straight-after-HS route.
So, what I'm getting at is, don't rule out school in the US as a very good next step along the way to get where you want to go.
There are ways to get to Japan. The Monbukagakusho undergrad scholarship is now open to applicants from the US (it wasn't when I was graduating from high school), but it is very hard to get. I think it is much harder than the postgrad research student scholarship.
There's also the senshu-gakko (special training school) category, which is not offered to many recipients each year comparatively, but it is an option, and music might be a field of study that they would accept for that. As far as I know, those are basically the only way you can get a full scholarship for school in Japan.
So if you really have your heart set on Japan, give that a shot, but definitely be prepared to study in the US.
Besides, college in the US can be a lot of fun, and though a lot of it is bullshit (gen ed requirements, etc) it's generally worth your time.
My advice would be to go to school in the US, study Japanese, spend a year in Japan, have a blast in both places along the way, and then set your sights on Japan afterwards if that's really what you want to do.
And, go wherever there is a good career for you, even if it isn't Japan. I think you'll likely be much happier overall that way.