Dix, Gregory. The Shape of the Liturgy. 2nd ed. London:Continuum International Publishing Group, 2005 (republished from 1945 original edition).
Chapter 15, “The Mediaeval Development.” pp. 546-612
As is his habit, Dix divides liturgical developments into the Eastern and the Western churches, treating those of the East first. “The main lines of all the Eastern traditions had been reached before the end of the fourth century, and after this the process in all of them is no more than one of adjustment and development of detail” (Dix 2006, 546). The division between East and West grows in clarity by the end of the sixth century. In the East there was a strong effort to enforce uniformity to the leadership of Byzantium (Ibid.). The rites developed in the East until the ninth century, still drawing on the earlier elements found in Syria and Jerusalem.
“The Western development is more complicated and diverse and continued for much longer” (Ibid., 549). The collections of rites did not seem to be a catalog of historical development but rather a collection of the decisions made in various communities (Ibid., 550). Local practices were variable, within the overall confines of the historic liturgy. Dix treats various regions in order on pp. 551ff, giving very specific examples including the text of prayers. The developments in the eucharistic prayer were possible in large part because the congregants did not possess the text of the prayer. In locations where the prayer changed from day to day the congregation would not be likely to expect regularity (Ibid., 560). Dix also observes that rites were carried from one place to another due to migrations or wars (Ibid., 562). This was not only the case as regards the Gallican rites but also in the many different Italic variations (Ibid., 563ff). In the time of Charlemagne the Roman rites, used in the Carolingian court, gained prominence as Charlemagne forbade use of the Gallican rite, which was foundational to the non-Italic traditions (Ibid., 580). Dix observes further a general conformity to the Roman rite, voluntary and widespread, from about 800 to the Council of Trent (Ibid., 586). Dix finally discusses habits of position of the part of the liturgist as he gradually moved from behind the altar, the traditional location of a bishop, to in front of the altar, the normal location of any other elder (Ibid., 589ff). Various other changes in presentation tended to occur in the West. At the same time as these developments occurred, the overall quality of catechesis declined for the growing body of Christ (Ibid., 595-6). The laity tended to commune less frequently as clergy communed more often. This trend made communion something to be observed, rather than to be participated in (Ibid., 598).