Seconding St Olaf, especially due to the math/music combination. There are music scholarships (you need to participate in a band/choir but don’t have to major in it) as well as academic scholarships.
Another idea: Case Western Reserve. They are very strong in STEM, good music opportunities, and have a “whole college” philosophy meaning that if you’re admitted you can add or switch majors without restrictions (most public universities have restrictions to switching majors or being admitted to the major if it wasn’t the one on the application or require students to meet specific criteria.)