The repertoire of the so called Gregorian chant is based on a Roman sacramentary called Hadrianum, because Charlemagne asked Pope Hadrian I for a sacramentary to establish the Roman rite in the Frankish Empire arguing in front of Frankish cantores that his father Pippin III already tried to romanize the liturgy of the Empire (admonitio generalis 789). Through the synode of Frankfurt 794 the Carolingian reform became official and the cantores had to abandon the former Gallican rite and to learn a vast chant repertoire provided in the sacramentary. The amount of mass chant was ten times larger in comparison with the repertoire sung during the Divine Liturgy in the Hagia Sophia of Constantinople (cathedral rite).
Transmission of chant, canonized scripture, and poetry were part of an art of memory and clerics regard themselves as the champions of this craftship. The sacramentary provided the text of Roman chant without using any musical notation than ekphonetic interpunction. The fact that a more detailed notation was used since the end of the 9th century is surprising, because it was neither used by Jewish cantors, neither by Sufi musicians, nor Hafizes during the following centuries. Some chronicles of the 9th century report that Frankish singers corrupted the Roman chant. In reaction Frankish cantors invented Western neume notation and used scripture to control the repertoire which was fashioned as "Gregorian chant", as a divine inspiration of Pope Gregory the Great expressed in an illumination of the Hartker Antiphonary:
But Gregory lived 300 years before the neumes were invented as an evolution of the ekphonetic notation in the Frankish scriptoria, so he could not know the Saint Gall neumes written by the scriptores next to him. This hagiographic illumination transported a rather political message, because Gregory usurped the authority of the patriarch of Constantinople as King Charlemagne usurped later the authority of the Byzantine Emperor, coronated as the Emperor of West and East Roman Empire by Pope Stephen II during Christmas 800.
The Roman tradition was still based on oral transmission, and it was not codified into notation before the end of the 11th century. But the suspiscions against the Frankish cantores during the 9th century are confirmed by these late chant manuscripts: the Roman-Frankish and the Roman or Old-Roman chant are based on the same liturgy, but they both offer a constantly different transmission of the same liturgical chant repertoire.
Despite the fact that philologists are quite absorbed to reconstruct the diastematic (melodic) structure of the melos based on their knowledge of later notation, its early form makes evident that the melodic memory was not the main function of 10th century neume notation. Obviously there was an oral practice for the pitches, as Notker of St. Gall described it by the use of troping melodies. This means that cantors recognized the melodies by melodic phrases, transcribed and grouped by neume notation. The neumes show clearly the number of pitches used in the melody, but they were memorized note be note by underlaid syllables. The early neumes, "adiastematic" or "in campo aperto", inform about the phrases of the chant, providing the melos note by note, but without exact information about the intervals—with the exception that some additional letters sometimes define, if the following note is continuing on the same pitch, above or below. Despite this imprecision concerning pitch, especially the notations developed in the scriptoria of Lorraine (Laon, Metz) and Switzerland (Sankt Gall, Einsiedeln) are very detailed in performance practice, while they are using numerous ornament signs, accents to express a certain rhythmic or agogic value of a note, and special signs (liquescentes) for the sound of semivowels, which also give some information about the local pronounciation of the Latin words. Even recent researches still continue to discover more and more details of this notation.
In comparison with Byzantine Round notation the characteristics of Western neume notation are: a detailed note by note transcription of the formulaic phrases and no modal keys which refer the mode of the melos. It is evident that the oral transmission of the melodic structure was so precise, that a later modal classification according to the eight mode system (oktōēchos) could be deduced by an analysis of an obviously unknown melos.
For this modal classification a certain manuscript type called tonary was used which is older than any fully notated chant manuscript: The earliest testimonies can be dated back some years before the Carolingian reform. In the later chant manuscript these tonaries often served as an appendix. A tonary refers each mode by a characteristic intonation formula and its psalmody, and usually the incipits of some antiphonal chants used as refrain between psalm recitation follow. In some rare cases cantores testified their classification of the chant by modal keys, later written on the margin, or the whole chant manscript provided each chant fully notated in the order of the eight modes.
The conclusions made on this method of modal classification are: The cantores adapted with the tonary each piece of chant according to the eight mode system which was not inherent in the whole repertoire. This way the notation and its (unwritten) transmission allowed a cantor to learn a huge repertoire of unknown chant without any knowledge of its melos and of the local school or tradition behind the melos. During the 10th century, the Roman chant tradition represented by the institution Schola cantorum was already a patchwork tradition which combined for an extravagant liturgy examples taken from different regional traditions of Western and Eastern plainchant. In contrary to Byzantine notation no signs like phthorai were used to indicate transpositions, so the new and very complex form of written transmission was based on a simplification of music theory and its main concern was a reliable and unambigious modal classification—a subject, which never interested a Greek psaltis. This simplification was due to the transfer that was offered to every cantor of the Frankish empire.
During the 11th century the early notation became unreadable after 120 years and the oral note by note transmission was replaced by an additional letter notation which refer the positions of the Boethian diagramm (including dieses to sharpen the half tone between E-F, a-b flat and b natural-c):
In a second step diastematic forms of notation were developed which tend to place a sign in a vertical position according to its pitch class. One or more horizontal guide lines support the vertical orientation. The evolution towards staff notation in the late 12th century was accompanied by a decline concerning all the details which were refered in the early neume notation of 10th century.
The presentation here emphasizes early chant notation and is focussed on an adequate performance of all the ornamental details and microtonal shifts, which are part of the modal practice and which were discovered by recent researches, when Western academic musicians became more familiar with the microcosmos of sound and pay more attention to medieval treatises whose authors sometimes tried to describe these details. Though we cannot be entirely sure about the exact meaning that some ornamental signs once had, this page does not only want to introduce into Western neumes, but also to encourage other musicians to cultivate their own understanding of these modal details of monodic chant.