structural:scholar_edition, information:extraction
Origins of mature plainchant

The Gregorian repertory was further systematized for use in the Roman Rite, and scholars weigh the relative influences of Roman and Carolingian practices upon the development of plainchant. The late 8th century saw a steadily increasing influence of the Carolingian monarchs over the popes. During a visit to Gaul in 752–753, Pope Stephen II celebrated Mass using Roman chant. According to Charlemagne, his father Pepin abolished the local Gallican Rites in favor of the Roman use, to strengthen ties with Rome. Thirty years later (785–786), at Charlemagne's request, Pope Adrian I sent a papal sacramentary with Roman chants to the Carolingian court. According to James McKinnon, over a brief period in the 8th century, a project overseen by Chrodegang of Metz in the favorable atmosphere of the Carolingian monarchs, also compiled the core liturgy of the Roman Mass and promoted its use in Francia and throughout Gaul.

Willi Apel and Robert Snow assert a scholarly consensus that Gregorian chant developed around 750 from a synthesis of Roman and Gallican chants, and was commissioned by the Carolingian rulers in France. Andreas Pfisterer and Peter Jeffery have shown that older melodic essentials from Roman chant are clear in the synthesized chant repertory. There were other developments as well. Chants were modified, influenced by local styles and Gallican chant, and fitted into the theory of the ancient Greek octoechos system of modes in a manner that created what later came to be known as the western system of the eight church modes. The Metz project also invented an innovative musical notation, using freeform neumes to show the shape of a remembered melody. This notation was further developed over time, culminating in the introduction of staff lines (attributed to Guido d'Arezzo) in the early 11th century, what we know today as plainchant notation. The whole body of Frankish-Roman Carolingian chant, augmented with new chants to complete the liturgical year, coalesced into a single body of chant that was called "Gregorian."

The changes made in the new system of chants were so significant that they have led some scholars to speculate that it was named in honor of the contemporary Pope Gregory II. Nevertheless, the lore surrounding Pope Gregory I was sufficient to culminate in his portrayal as the actual author of Gregorian Chant. He was often depicted as receiving the dictation of plainchant from a dove representing the Holy Spirit, thus giving Gregorian chant the stamp of being divinely inspired. Scholars agree that the melodic content of much Gregorian Chant did not exist in that form in Gregory I's day. In addition, it is known definitively that the familiar neumatic system for notating plainchant had not been established in his time. Nevertheless, Gregory's authorship is popularly accepted by some as fact to this day.