Thanks- that all makes sense. My daughter was unsure as well and so she applied to all the options and decided in late April 
With auditions involved, she kept the conservatories down to 4, and two college, but of course many do more.
The other factor, I think, is that your son is a horn player. I know kids who taken a general music major OR who major in something else entirely, and take a music history class they loved, sing in an a cappella group that travels abroad, take cello lessons, etc. etc, and enjoy- at an LACw/out a BM I think some of these LAC’s have very strong music departments even when there isn’t a performance aspect to the program. But not for horn (though there may be a great teacher available).
Good luck! It ain’t easy getting clarity but it will come.