Principi Apostolorum Petro §13

¹³ The artistry introduced by Blessed Ephrem added dignity to sacred matters as Theodoretus stresses. The metric rhythm, which our saint popularized, was widely propagated both among the Greeks and the Latins. Indeed does it seem probable that the liturgical antiphonary with its songs and processions, introduced at Constantinople in the works of Chrysostom and at Milan by Ambrose (whence it spread throughout all of Italy), was the work of some other author? For the "custom of Eastern rhythm" deeply moved the catechumen Augustine in northern Italy; Gregory the Great improved it and we use it in a more advanced form. Critics acknowledge that that "same Eastern rhythm" had it origins in Ephrem's Syrian antiphonary.