haven't done so already, read the post here. http://talk.collegeconfidential.com/...xperience.html
I've never seen a better overview. Anywhere. Period.
For most institutions, except the strict conservatories, music performance majors are granted admittance based on the strength of the audition, and there is an additional instutional academic threshold that must be met. Some institutions bend the academic threshold for top auditioners, at others, it can be a line in the sand, and will not be crossed. In general, academics play a minimal role in conservatory programs.
The basic difference between a BM and a BA in music is that a BM is akin to a BS, with more practical, hands on "technical" type courses that in effect have you put theory into practice (performing organizations, ensembles, probably another year of music history, and theory beyond the BA curriculum.
The BA may be a bit lighter in overall credit requirements than a BM, and there will be less required music courses within the BA than the BM to fulfill degree requirements. In general, there may be more liberal arts/non-music electives within the BA as opposed to the BM.
A BA in music may or may not have an audition requirement, a BM most surely will. Also, institution specific is the policy regards lesson times, faculty assignment, lesson cost. Most BM's will have an hour long private lesson weekly, normally with a faculty instructor plus a studio class, costs are normally part of the tuition; BA's may be relegated to a shorter lesson time, possibly be taught by a GA or TA, or have off-site lessons with non-faculty instructors. The program may cover the cost, subsidize, or be an additional fee beyond tuition. It's pretty school specific.
What exactly do you want to do with music? Play professionally, on a high amateur level, teach publically or teach privately, or just continue to play in college? It's hard to offer suggestions without knowing a bit more about your proposed path and goals.