I think it’s pretty well covered in your other thread about best LAC music departments. If you’re looking for absolute top-tier academics/selectivity and strong music, Vassar and Wesleyan (already on your list) are solid and you should probably add Williams. Anecdotally (i.e, from folks on CC) I’ve heard some good things about Macalester and Davidson as well. I see you’ve got Brandeis and Tufts on your list, too. Not true LACs, but I’ve heard good things about their programs (though does Tufts involve getting yourself to one of their nearby conservatories? Not sure about that).
A notch down in selectivity, but probably a notch up in music, you’ve got schools like St. Olaf, Lawrence, Gettysburg, and U of Puget Sound. All of those have large, accredited departments that allow non-majors to participate. Skidmore (already on your list) also looks quite strong.
One more notch down in selectivity and you’ve got schools like Rollins, Luther, Concordia, and all the others I listed in your other thread.
Anyway, I’m mainly rehashing stuff you already know. If there are other hidden gems out there that got absolutely no mention on your other thread, then they’ve eluded me as well. Actually, maybe I should throw out one more: Trinity University in Texas. Their music doesn’t look outstanding, but based on the fact they offer a B.M. degree and had a decent number of music majors (you can see number of majors by discipline at http://nces.ed.gov/collegenavigator), it’s at least above average. It doesn’t show up in the LAC lists because they classify themselves as a “regional university”, but it’s every bit as much an LAC as Wesleyan or UPS – 2300 undergrads and a handful of grad students. It doesn’t have a very high national profile, but it seems like a terrific school.