Legend suggests the St. Gregory the Great (d. 604) heard the 1st 3 strains chanted by angels on a specific Easter morning in Rome when he walked barefoot in a fantastic spiritual procession and that the saint thereupon extra the fourth line: “Ora pro nobis Deum. Alleluia.” This Marian hymn https://vitapronobis98642.free-blogz.com/78532246/vita-pro-nobis-secrets