It’s funny because most of the BA programs we investigated did not have auditions. Not for admission. Maybe for entrance into extracurricular ensembles etc.
Is the only reason for doing a BS to avoid gen eds? STEM majors are usually BS’s as you know. A BS can be intense and combining with another major is sometimes difficult.
I would think he could pick schools based on the usual factors of location, size, academics and vibe, then talk to the music department. I would not necessarily expect an applied music faculty at all schools, but for lessons, schools will often provide a list of teachers in the area, and some will give credit for lessons and extracurricular music activities.
So it may not be necessary to eliminate schools that don’t list faculty for your son’s instrument.
In a school with a BM program, it may be that the listed faculty will not be available to a BS student. It varies. Sometimes grad students teach and that is what is offered to undergrads.
Unfortunately you really have to investigate each school and calling or emailing the departments can be helpful.
ps on this forum I have read that all state is not the best measure of chances for admission, but I could be wrong…maybe he could do a longer summer program if affordable