Dr. Edward Cairns's "Christianity Through the Centuries," 169ff.

Hierarchal and Liturgical Developments, 169-176. Between 313 and 590, the Roman bishop acquired primacy of honor over Constantinople, second in honor. Jerusalem, Antioch, and Alexandria were also reckoned as metropolitan centers of leaders. As for Rome, Leo the Great and Gregory 1 were two notable advancers of this supremacy. Leo (4th century-461 A.D.) was able mollify and divert in 410 A.D. the wholesale destruction of Rome from Alaric and his marauding Visigoths.  Leo was the first Bishop to be called “Papas” (171). Romish monks, working up north, furthered Roman hegemony. Dr. Cairns notes the 314 Council of Arles to deal with the North African issues of Donatism (we'd add that 3 English bishops attended). As for liturgical changes, we would note Augustine’s comment that there were multiple liturgies in use. Ambrose in Milan introduced antiphonal singing that had spread from Antioch. Art, images, and colors entered churches over time, although there was opposition. Liturgies, as they do, became more complicated with memorials to martyrs and notably saints. Gregory 1’s Canon of the Mass slightly shifted the Communion to a “sacrificial nature” (173). Seven sacraments grew in importance in this period. Veneration of saints turned from respect and reminiscence to invocation of departed saints, including developing Mariolatry. This era also saw great preachers like Ambrose, the Cappadocians, Chrysostom, Augustine and others.