How difficult is it to get into the music schools at Oberlin, USC, Boston University, U Michigan, UCLA, and Emory?
Emory is different from the others in that it does not have a BM program. It is a liberal arts program (BA) with performance, composition and research strands http://music.emory.edu/home/academics/index.html
BA programs are usually 1/4-1/3 music classes with gen eds and electives forming the rest of your studies.
Auditions there happen in the fall semester, and are open to everyone, whether a music major or not. This is true for ensembles and lessons. http://music.emory.edu/home/audition/index.html
You do not audition for admission to Emory though you could send a music supplement with a recording or video, a music resume and letters of recommendation from teachers or directors.
The other schools on your list have BM conservatory type programs with 2/3-3/4 classes in music. (Actually UCLA also has only a BA but it is more like a conservatory with auditions for admission.) They are selective because applicants generally want total immersion in music and have studied for years to get there. Maybe that’s you!
You can do a BA and major in music at most schools that offer a BM, but you need to check carefully whether the opportunities are as good for the BA students as for the BM students. Many BA programs- but not all of course- do not have auditions for admission.
You have to read websites carefully and don’t be shy about asking questions.
Specific to Violin :
BU wasn’t that hard to get into (regional audition in LA via recording), accepted.
Oberlin is fairly competitive, no screen video was required (2018), S skipped audition but got accepted in Physics program.
UCLA, fairly competitive, S got prof he wanted plus generous scholarship (in-state already)
USC, extremely competitive, S got top choice prof, some scholarship, top choice school, attending.
UMich - not sure how competitive for violin, but GPA bound, S applied but withdrew 'cause of other offers.