TBT-
If you are correct, then:
1) Why does he davka say ???? ?????? Why not ???? ??????
2) You are willing to say that the tune inherently carries with it a bad ???. Isn’t it just as, if not more ?????? that ????? ?? does too? I see plenty of people covering their babies ears when someone says a not nice thing, perhaps it is a shtus, but why do you think it is more ?????? that the bad ??? is coming from the tune than from the words?
3) Regarding what R’ Chaim supposedly said, I am intrigued. There is a famous Yerushalmi* that says that R’ Yehoshua ben Chananya’s mother would bring him as a baby to the Beis Medrash in order that he should absorb the sound of Torah learning. How would he answer that?
I already demonstrated that the Mishnah Berurah himself is matir using non Jewish tunes in davening, and over there he does not bring this problem of ???? ?????. This too leads me to believe that it was the words that he held is a problem. And even if not, from the fact that he doesn’t bring it l’halacha over there and instead simply quotes the Bach that it is mutar, is clear proof in my opinion that he did not hold of it as a halacha.
As for heeding the advice of the Shelah and the Chafetz Chaim, first of all I don’t even know that they gave the advice you claim they did, and second of all being that even on the tzad they did, it was not said l’halacha, so of course, no, one is not mechuyav to heed their advice. That’s why it is called advice, and not halacha.
*I don’t have the exact makor, but it is quoted here: link to citation removed, sorry.