My middle son sounds somewhat similar. He was/is conservatory level as a cellist, but wasn’t interested in conservatories. He did a ton with music including a lot of professional work (local professional theater companies, his own cello duets, a quartet that did gigs, and so on), solo work with his orchestra, and lots of service (fund raisers and the like). His test scores weren’t as strong (2230 SAT; 730 SAT II math, 710 SAT II Lit), and he didn’t have APs. He did have dual-enrolled classes (39.5 units), but nothing terribly spectacular (Calc I, Physics, English 105, Java and Italian I were his highest levels).
He had some awards/honors (his robotics team won a lot of awards; National Merit, Elks Foundation scholarship, and so on), but not too many.
He did not have a perfect GPA in his college classes, either. He applied to about 7-8 “top” schools (schools that meet 100% of need). I did not consider him particularly strong because of weaker course rigor, imperfect GPA, and no APs. He was shooting for just one affordable school.
He got into exactly one of his reachy-reach schools (WL at two), and that happened to be one of the two Ivies he applied to. He had no expectations of getting into any school, so this was a huge, huge surprise. The breakdown admissions-wise was this:
Admit rate < 10% Rejected by 2, accepted by 1
Admit rate <20% Rejected by 2, WL by 2 (eventually rejected)
Admit rate < 30% WL by 1 (eventually rejected), accepted by 2
Admit rate < 40% Accepted by 2
I would say your son should apply, but have a good sensible list of reach, match and safety schools.
As far as how to show his musical pursuits: both my boys did music supplements and had music resumes, and so should your son if he’s conservatory level. Even if he’s not going to major in music, he should absolutely submit a supplement. I believe that’s one reason my son got admitted to his college. He got a very generous music scholarship from U Rochester, as well.