Yeah, but he finally and all Protestants accepted the Catholic New Testament Canon.
It is funny how most Protestants don't even know why their founding fathers did what they did, especially when it comes to Scripture.
Well strictly speaking the New Testament canon is of Orthodox origins, since it originated with Pope St. Athanasius of Alexandria* in his 39th Paschal Encyclical, and was later picked up by the Roman church and most other churches, the three exceptions being the Church of the East, which never added the books not a part of the original Peshitta, which were added to the Syriac Orthodox Peshitta by Mar Philoxenus of Mabbug, although these days their official position is they recognize them as canon but do not read them liturgically, and then the Armenians have 3 Corinthians, and some Ethiopian bibles, those with the “Broad Canon” have the
Didascalia (a book of church order probably dating to the late first century, similar to the
Didache) at the end of the New Testament (to my knowledge this is the only difference between the Broad and Narrow Canons, with both having Jubilees, Enoch, etc in the Old Testament).
* In the fourth century, only the Bishop of Alexandria was styled Pope; this would not be adopted in Rome until the sixth century. Furthermore, in this era the churches of Alexandria, Antioch and Jerusalem were autocephalous, with Rome being primus inter pares but not primus sine paribus as it is now in relation to the Eastern Catholic churches, as attested to by Canons 6 and 7 of the Council of Nicaea, and also the failure of the Roman legates at Nicaea to get the Council to mandate clerical celibacy, which has always been limited to the Church of Rome. The Church of Rome in that era, between Archbishop Victor and Archbishop Leo I was also the most conservative, never having a heretical bishop until the infamous Pope Honorius I, who advocated Monothelitism, which is officially regarded as a heresy by the Roman Catholic Church, which participated in the Sixth Ecumenical Council.
However, Pope St. Gregory I Dialogos, deservedly called The Great , along with Archbishop St. Celestine, who allied himself with Pope St. Cyril of Alexandria, were, along with Pope St. Athanasius of Alexandria, Patriarch St. Ignatius of Antioch and Patriarch St. John Chrysostom of Constantinople, the best leaders of the autocephalous Early Churches. Jerusalem also had Patriarch St. Cyril, who was good, and there was Archbishop Cyprian of Carthage, also very good. However, most of the other bishops and archbishops we venerate from the Patristic era were not the rulers of autocephalous churches, for example, St. Basil of Caesarea, St. Gregory the Theologian, St. Gregory of Nyssa, St. Serapion of Thmuis, St. Ambrose of Milan, St. Irenaeus of Lyons, St. Polycarp of Smyrna, St. Epiphanius of Salamis, and the beloved St. Augustine of Hippo, were members of the Holy Synods of the autocephalous churches of Constantinople, Alexandria, Rome, Antioch, and Cyprus.
However, in terms of their contribution to the music of the church, St. Ignatius, St. Ambrose and St. Gregory the Great were the most important, because the great martyr of Antioch invented antiphony, the catechist of St. Augustine imported it to Milan resulting in it displacing monotone except from the Low Mass, which was sung in monotone for most of the first millennium before being said almost silently, as is now the custom in the traditional Latin Mass, and also St. Ambrose and St. Augustine cowrote the hymn
Te Deum Laudamus, one of a handful of hymns of the early church I regard as credal, and finally St. Gregory the Great gave us Gregorian Chant, inspired by the eight mode Byzantine Chant. Personally I prefer Gregorian, Ambrosian and Mozarabic Chant to most performances of Byzantine Chant, with only the Bulgarians singing it in a way that I enjoy. West Syriac Chant also uses eight modes which are arranged differently than the eight Gregorian modes.