What constitutes a "Protestant song"?
Lacking in substance, for one thing.
One writen by Martin Luther, or John Calvin. They didn't used to be allowed. They were the only things I missed after I converted in 1958. When we first started having hymns in the Catholic church (Low Mass) they seemed unsingable to my ear. Whole orders of priests, monks, and nuns wrote "new" hymns after 1965. We are still singing them today, and they seem to have relaxed the rule against "Protestant" songs.
However, at Newman Club at the University of CA, Berkeley, the priests used the "Congregational High Mass". It was sung all in Latin and sounded like Gregorian chant to me. I loved that. The space where they said Mass was upstairs. If you were a little bit late and they had started before you cimbed the stairs, the music afting down the stairs was simply heavenly.
I never found another church, after I married, that used that Mass, and I really missed it.
Amazing grace. One of my favorite songs but theologically wrong.
Not so much “protestant” —didn’t hear many Charles Wesley hymns — as banal tunes and lyrics meant to copy the “folk”music”of the day. More than that, they were discordant with the tone of the English liturgy, as most Anglican music is not. As for the guitar music, I am reminded very time I hear them, played side by side. how much better Spain music than English version of the same songs. You need a guitar musician with the talent of Glen Campbell to make words and music come together properly, and I can’t think of any Catholic guitar tunes of the period that were anything except bad.