Gregorian is the name commonly given to the entirety of Latin monodic chant in the Catholic Church.   Books of “Gregorian chant” (Graduals or Roman Mass books) call Gregorian a repertoire extending from chants belonging to the first centuries of the Church, through the great Kyries of the eleventh century to the most common Credo and Masses of the seventeenth century.  A more specific and scholarly use, however, is to call Gregorian all the the chants contained in the manuscripts from the end of the ninth, from the tenth and eleventh centuries which are called Antiphonaries, Cantatoria, or Graduals, noted with neums and originating in a geographical area including France, Switzerland and the neighbouring regions of West and South Germany, as well as Northern Italy.

    Within this repertoire, there is an attempt to distinguish a store of ancient pieces considered to date from before the ninth century.  The looseness of these definitions stems from the ambiguity of the term “Gregorian chant”, which does not correspond to the repertoire it is supposed to designate. Scholars have sought to attach this chant to Pope Gregory the Great, who died in 604CE, and hence to the churches of the town of Rome.  But this pedigree, which has thrown up thorny problems for musicologists (Apel, Gastoué, Gevaert, Hourlier, Hucke, Huglo, Morin, Stäblein, Toloza…) is in fact a mere legend, and is contradicted by the witness of history and manuscripts.  The Pope’s name was imposed by the so-called Gregorian “restoration” at the end of the nineteenth century, but it masks the manifold reality of this chant and the traditions which make it up.

    It is more accurate to speak generally of the grand Ancient Christian Chant in the West. 
This was shaped from the fourth century onwards on a common liturgical basis (originally there were Jewish, Egyptian, Syriac and especially Greek influences) and with the flourishing of western Christian culture on the various expressions of  the Latin tradition, this chant developed (as was also the case with liturgical usage)  in several independent regions with relations between them (for instance, usage in Gaul and usage in Rome).  The chief liturgies in the West were as follows:  for Italy - southern Italy, Rome, northern Italy (Milan was the capital of the Empire in the fourth century) and Aquila;  North Africa (Carthage);  Spain (Toledo);  for Gaul – Aquitaine, Provence (Narbonne, Marseille, Arles, Vienne), the Lyonnais (Lyon, Autun), Belgium and Germany (Trier, another former capital of the Empire);  Great-Britain, and, as early as the sixth century, Ireland.  Traditions of chant are clearly linked to regional liturgies;  four repertoires and styles of chant are well-known:  that of Milan, called Ambrosian, that of Rome, also called Old-Roman, the Mozarabic (Old Spanish and Visigothic) which unfortunately is still indecipherable, and the Gallican, belonging to north-east and south-west Gaul.  This was based on a specific Carolingian liturgy and has given rise to what is inaccurately called Gregorian.  The liturgy was a mixture of the traditions of Rome (the written tradition and the order of the liturgy) and of Gaul (the oral tradition and the chant) and was developed at the end of the eighth and during the ninth century under Pepin the Short, and particularly by Charlemagne.  Under the influence of the Carolingian Empire and subsequently of the French provinces and the provinces of the Holy Roman (German) Empire, it progressively (from the ninth to the thirteenth century) ousted all other liturgies including even those proper to Rome, except for the Ambrosian rite of Milan (the final eradication of local traditions was to take place in the nineteenth and twentieth centuries).

    With Gothic art, Ancient Chant, except in certain monasteries, was relegated to the role of plainsong, in contrast with part-singing which arose from a less learned popular tradition, albeit one which developed with writing.  The Renaissance was to impose its own style and Gregorian chant reduced to “tunes” no longer had any meaning.   It is to the nineteenth-century French Benedictines that we owe an attempt at restoration, marked by the publication of a Gradual (Solesmes, 1883).  Unfortunately the living tradition was lost, and with it the notions of ancient scales, just intonation, modes in the sense of the ancient oral tradition, and the very conception of sacred art (and not merely religious art, i.e. religious subjects treated by secular means) was long lost.

Art and sacred chant
    The essence of the repertoire is sacred chant, in the context of the liturgy which is the sacred art par excellence.  This means an art which is founded on and must effect a genuine relation with the divine.  Its origin is the illumination of consciousness in the contemplation of the divine, for in the contemplation of the one God the true rhythms and numbers of Music and Dance are revealed (the dance is that of the soul in this contemplation, as St Augustine, reasserting the tradition of antiquity, pointed out [De Musica, VI]).  Sacred Art is founded on the numbers, the rhythms, the consonances, proportions and movements resulting from such contemplation;   these divinely inspired movements are represented in liturgy by architecture, image, light, and incense, and they are powerfully transmitted by chant, beyond even the power of words;  they awaken the divine part of the soul, in order to establish it in an essential relation with the invisible.  For chant in precise intonation – acting directly on the body through the intervals, the vibrations and the syllables, and on deep consciousness by the timbre of voice - is the reflection in sound of psycho-physiological states which Antiquity called movements of the soul; this is what “mode” corresponds to.  Chant, then, can transmit and induce such states and has in particular the power to convert.   An interpretation of chant seeking authenticity today must be rooted in this ancient and fundamental concept of sacred art.  When such a conception of chant was thus understood and put into practice, Christianity spread irresistibly by Christ’s words of love, but also by the beauty of the liturgies in which these words were clothed.

    For thirty years now, Iégor Reznikoff has been undertaking a restoration of Ancient Christian Chant in this sense.

Ancient Christian Chant and its interpretation
    The interpretation of chants belonging to the ancient Christian repertory in Latin is based on:

a) a study of the manuscripts noted in neums from the ninth, tenth and eleventh centuries of Western Christian chant, from Rome, from Gaul (the so-called Gregorian), from Milan, from Spain, etc.;
b) close study of the foundations of sacred art and ancient Christian liturgy;
c) attentive listening to and constant study of living traditions related to Ancient Christian Chant (Christian chant of the East, learned spiritual music of Turkey, Iran and India, but also some survivals in country districts in the West);
d) practising chant with a monochord as used in antiquity and high medieval singing-schools, with its pressing demand for justness in natural resonance;
e) practice within the resonance of buildings, especially Romanesque churches.
Such practices enable one to approach the exactness of the ancient intervals, understand  the natural scale with its unequal tones, and the nature of the Pythagorean scale which remained a reference point from Antiquity to the Romanesque period;  one may also begin to understand the notion of mode.  This notion is devoid of meaning if one sings according to modern western scales, with their fixed, tempered intervals, for the notion corresponds to psycho-physiological states, and the resonance of sound in the body characteristic of these states, which Christian Antiquity continued to call movements of the soul.
    It should also be noted that the repertory of the Gradual, for instance the great alleluias, graduals, offertories, is above all a soloist’s repertory, whether a Cantor or a Master-singer, who takes on, as readers do, a role in celebration and praise.