Very strong applicant. One thing to take into account: Who else at your school will be applying Harvard/Princeton and how will you fare if you are compared to them?
Also, have you thought about sending supplements? (Videos, portfolios) I think they would not only give full proof of your achievements in art and music, but also strengthen your application even further.
As always, if your essays are solid and recs are good, I think you should have a very strong chance.