Legend states the St. Gregory The nice (d. 604) listened to the first 3 strains chanted by angels on a particular Easter early morning in Rome even though he walked barefoot in a great religious procession and which the saint thereupon additional the fourth line: “Ora Professional nobis Deum. Alleluia.” https://dores-nos-nervos87542.blogprodesign.com/52875310/vita-pro-nobis-fundamentals-explained