jbaldy22 – You’re 100% right! I must have assumed that that was the reason when I originally learned it, and in my head I remembered the MB saying it. Interestingly, I just looked at it again; the Rema uses the word “miranen”, which seems like it’s only a problem if he sings; merely listening to them is not a problem.
I believe I did make note of the fact that this was referring only to religious songs, as you said.
WIY – I never meant to use this as a mekor to listen to non-Jewish music; I was merely noting that the MB does not add on (as he often does in similar situations) that either way it is assur.
For a discussion on kol isha, see the Mishneh Berurah (75:17) where he initially states that kol isha of a p’nuyah (single girl) is muttar. He then modifies that to exclude Jewish girls (because of chezkas niddah) and non-Jewish girls (because of ervah). So only a Jewish single girl who is tahor would be permissible, and even then only without any thoughts of arayos. Basically, kol isha is assur.
Personally, I do believe the theory that music goes into your soul (maybe a devarim shebileiv-esque theory), and some of the best musicians were some of the most messed-up. (Think Freddie Mercury, Michael Jackson)