While there is a common core to historic Western Christian liturgy, there is also considerable diversity. Rites differed from region to region and from place to place. Regional improvisations on the basic framework of the liturgy led eventually to a proliferation of liturgical books in the Western church, with many variations even within the same regional traditions.
In origin, evolution, and spirit, the liturgical tradition of the Western church is complex and diverse. What is known as the Roman rite was only one of several Western rites which existed between the fourth and sixteenth centuries; the others are known as the North African, Ambrosian, Spanish, Gallican, and Celtic rites.
In matters of worship, local churches were free to develop their own forms and often did so in conjunction with the churches of the same region under the authority of the metropolitan bishop who served as primate of the region or “diocese” as it was termed in the Roman Empire. The bishop of Rome, as primate of the part of Italy extending south of the city of Rome (i.e., Italia suburbicaria), had the right to insist that churches in that region conform to Roman usages (see letter of Innocent I to Decentius of Gubbio, 19 March 416). In like manner, the bishop of Milan as primate of Italia annonaria, the bishop of Carthage as primate of Africa, the bishop of Carthago Nova (until 531) or of Toledo (after 531) as primate of Hispania, the bishop of Arles as primate of Septimania, and the bishop of Lyons as primate of Gaul, could convoke synods and insist upon adherence to liturgical canons.
Until 1080, the Roman see never attempted to control the liturgical observances of churches outside of Italia suburbicaria. Indeed, because of the Lombard invasions, its sphere of liturgical influence was limited to the narrow corridor which joined Rome and Ravenna. As a matter of fact, the bishop of Rome was well aware of the need for diversity of forms to suit the temperament of different peoples. In 597, when Augustine of Canterbury wrote to ask Gregory I why the churches of Gaul and of Rome had different usages and which rite to use for the newly converted Angles, the pope replied:
You should carefully select for the English church whatever is most able to please almighty God, whether it comes from the Roman, Gallican, or whatever church you may find it.… Things ought not be loved because of the place from which they come, but because they are good in themselves. Therefore choose elements that are reverent (pia), awe-inspiring (religiosa), and orthodox (recta) from each and every church and arrange them as in a little book in accord with the mind of the English and so establish them as custom (Monumenta Germaniae Historica, Epistolae 2, 334).
Although most of what we know about the individual rites can be discerned only from the evidence of extant liturgical texts and artifacts, the various Latin rites emerged when improvisation was still predominant, and long before the date of the oldest surviving manuscripts. The practice of improvisation, however, presupposed the faithful observance of certain canons, guidelines, or principles which were transmitted in the local church from one generation to the next. At the core of this liturgical patrimony was the structure of the service, the framework for improvisation. In all the traditions, the first composition of written texts was nothing more than a new type of improvisation. A set of texts was prepared for a specific celebration and afterward placed in the local archives as a record of the celebration. Fifth-century Rome witnessed the production of a great number of variable texts for the Eucharist, the composition or editing of euchological texts for the administration of the sacraments, and for use at the liturgy of the hours. By the end of the same century, samples of this written improvisation had found their way to northern Italy, southeastern Gaul, and northeastern Spain, inspiring a veritable explosion of euchological creativity throughout the West, giving additional impetus to the emergence of the local rites, and leading eventually to the compilation of the numerous liturgical books of each tradition (sixth-ninth centuries).