Many old "traditional" hymns have been changed in OCP hymnals. Two egregious examples (there are many) are Good Christian Men Rejoice to Good Christian Friends Rejoice and Come Thou Fount of Every Blessing to Sing a New Church into Being.
I go to a Catholic Church, so it stands to reason I would notice these changes made by OCP. As I said, that was my FIRST thought, later contradicted by the evidence.
No offense intended.
"Sing a New Church" is a new set of lyrics to a traditional melody. "Come Thou Fount" was probably also a new set of lyrics, on what was originally a popular song.
Why are Catholic Churches even using Protestant hymns? I hate the intrusion - it’s wrongheaded. And I speak as someone who thinks Protestant hymns are often very beautiful as well as very Americana. Years ago, my mother made me walk out of a Mass when the choir burst into “Onward Christian Soldiers”! It’s a fine song but not a Catholic hymn.