<p>I don’t know that I would agree with <em>most</em> profs having a BA background instead of a BMus background, at least, if he meant that same was not obtained at a conservatory, at all. McSon’s theory teachers have collectively been pretty evenly divided from a wide range of conservatories and then masters/phd. Eg. his prof last year was from Julliard and also held a masters in piano. Another prof of his studied at CIM. That said, I think one of his favorites was from University of Chicago, which is not a “school of music” but does have an awesome composition program. So I don’t think you can categorically say that most music theory profs started with a BA.
Logically speaking, BA programs generally aren’t designed to cover the same depth as a BMus or BMA, the latter of which have a highly programmed sequence which allows for (and requires) fewer general distribution credits. I guess it depends on the circumstance, since you could generalize with a BA and then obviously concentrate with the masters and phd, so perhaps it truly doesn’t matter which road you start on.</p>
<p>One further note re the OPs mention of a major-minor or dual degree. That is possible at UMich via the Bachelor of Musical Arts program, which is another avenue to theory study at the undergraduate level.</p>
<p>EDIT: I lied. Current favorite theory prof actually studied at Princeton and Yale, so yes, he would have started with a BA. But they do seem pretty evenly split at his particular school.</p>