Okay. So I’ve done a pretty good amount of music ECs in high school (like a lot, for the entirety of my high school career). If I’m applying to a selective/top school, will they think less of them since I’m not planning on being a music major?
No
Colleges won’t think less of you. In fact, spending a lot of time in one area can reflect passion, which is good on an application. If you can, maybe try to also get invovled in something that relates to something you might want to study instead, but that’s not critical.
To answer your question shortly, no, it won’t reflect poorly on you at all.
Ditto