If a student applies to, is admitted, and enrolls in LSA, can he/she apply to the Music school once enrolled at Michigan? Or does the Music school at Michigan only admit students who apply straight from high school?
No, you can always audition during the audition cycle. I know a student who got into LSA, but was rejected as a music major as a senior in college, so she reauditioned the next year, while a freshman in LSA, and was accepted as a music major. So the following year, as a double major, she was basically a sophomore in LSA, but a freshman in the SMTD. She also had a friend who tried to do that, but was rejected once again as a music major. It’s tough to do, but it can happen.
Sanx Saxlady! 
Ha, just read my answer, I meant senior in HIGH SCHOOL in that second sentence…but I think you figured that out, Alexandre!
Sure did! It helped a lot.
Not sure!