I posted this on another thread (and would also ask you to think about your need for a practical “backup.” It really is okay to major in music only, whether for BM or BA!):
First, have you read the Double Degree Dilemma posted closer to the top of this forum? It might be helpful.
What kind of involvement in music do you want? Mainly lessons and performance, or do also want theory, music history, and music technology etc?
Computer science and music are both intensive and sequential curricula so double major would be tough. I think you are wise to either do double degree, OR major in computer science at a school where there are lessons and performance up to your level, as extracurriculars (and many schools will give credit for lessons and certain performances).
If you are applying for a BA or BS program, be aware that submitting a music supplement with recording, music resume, and letters of recommendation from music teachers or directors can sometimes help your application.
There are many schools with double degree programs for music. If you are sure you want both BS and BM, rather than the extracurricular route:
Harvard/NEC (MM), Tufts/NEC (BM), Bard (conservatory requires double degree), Oberlin (look at their Music Studies program as well), Ithaca, Hartt / U. of Hartford, Bienen /Northwestern, Carnegie Mellon, Michigan, many state universities (check out SUNYs), Mason Gross/Rutgers, Eastman/Rochester (selective music), Johns Hopkins/Peabody (probably not as geared to double degree but possible) and many others.
Some music schools are more supportive of double degrees than others, but I am mentioning a few so you can investigate. Honestly there are a lot more…