GREGORIAN CHANT

The revival of monasticism in the 19th century by Dom P. gueranger of solesmes abbey and the concomitant revival in liturgical studies brought about a renewed interest in the history of Gregorian chant. This chant was seen as belonging to the golden age of the formation of Roman liturgy and thus as holding priority of place in the history of sacred music. Although terms such as plainsong or plainchant (cantus planus, unmeasured chant, in contradistinction to cantus mensuratus or rhythmically organized song) also are used, Gergorian chant has become the most popular term because it can be easily differentiated from ambrosian, mozarabic, gallican, and byzantine chant. Gregorian chant was first written down in the 9th century and has continued in unbroken use in the Roman rite to the present day. In each period of music history it has been influenced by the contemporary musical idiom, and constant attempts to find out what its original character was like have bee made during the centuries. Present scholarship has unearthed many problems that remain unsolved. More important historical perspectives have been opened up by: M. Huglo, H. Hucke, J. Handschin, B. Stäblein, D. Levy, D. Hughes and J. McKinnon. Valuable contributions have been made by E. Wellesz, Dom L. Brou, and O. Strunk on the relationship between Gregorian chant and other

Eastern and Western chants. Scholars such as E. Jammers, J. Vollaerts, S. Corbin, and H. Husmann have probed specific areas such as paleography, rhythm, rhymed Offices, drama, Sequence, and trope. Work on the medieval theorists has not ceased, and valuable reediting and interpreting of texts has been done by J. Smits van Waesberghe, H. Oesch, and H. Hüschen. A most comprehensive and complete study on Gregorian chant, bringing together all of the information thus far arrived at by scholars and offering a balanced judgment on recent theories, was made by Willi Apel (Gregorian Chant, Bloomington, Indiana 1958). This present brief survey of mid-20th-century scholarship indicates the renewed interest in the field and the areas that are the subject of most concern.

Problem of Origin. General histories of music had too easily assumed that Gregorian chant dates back to at least the 6th century and was put in its present form by Pope Gregory the Great (590 to 604). Although this theory was often seriously challenged (see F. Gevaert, Les Origines du chant liturgique de l'église latine, Ghent 1890), it persisted in vogue, carried along by centuries of tradition. It must, however, be recalled that the first manuscripts containing Gregorian chant came from the 9th century from the Frankish empire. Many of these manuscripts, especially the Graduales, contain a famous introductory trope, Gregorius praesul. It is a kind of Carolingian publicity technique to advertise the fact that the new chants were in the Roman style, the cantilena romana. It cannot be proved that Gregory the Great is the Gregory here alluded to, and the possibility that it refers to Gregory II (715 to 731) must also be considered. Even if one accepts the assumption that Gregory the Great is referred to, it remains dubious how much of the music that is first written down in the 9th century goes back to Gregory's time in an oral tradition.

Gregory's Role. What can be said with certitude concerning the activity of Gregory the Great is that he sought to bring order into the liturgical texts by compiling from various sources the antiphonarius cento. This could not have been done without reference to the music accompanying the texts, but about this nothing is known. His concern for music can be seen also in the founding of monastic groups to serve the basilicas and in the impetus he gave to the schola cantorum. The general principles of music-making that lead to Gregorian chant and especially the principles of formulae that form its psalmodic structure must have existed in his day, but there is no way of proving that any given piece of Gregorian chant goes back to that date. In the lists of popes in the Liber pontificalis, other pontiffs also are included as contributing to the history of the annual liturgical cycle (annalis cantus omnis ), but the lack of accurate musical examples from the period makes its impossible to assess the contribution of any particular individual to the formation of the chant corpus.

The Role of Rome. The problem of the origin of Gregorian chant is complicated by the difficulty of ascertaining the nature of chant at the Roman basilicas until the 11th century. It can be accurately documented that Roman chant from the 11th to the 13th century was not the same as Gregorian chant. Five manuscripts dating from that time contain a tradition that is unique. They are: Vat. lat. 5319, a Graduale from the last quarter of the 11th century; a Graduale dated 1071 and written for Santa Cecilia in Trastevere, now in the M. Bodner collection, Cologny-Genève, Switzerland; Vat. Bas. F22, a Graduale from the first half of the 13th century; Vat. Bas. B79, an antiphonary, 12th century; and British Museum, Add. 29, 988, an antiphonary from the 12th century. The theory that the tradition contained in these manuscripts dates back to the Carolingian period and beyond and is thus the "Old-Roman" repertoire has had strong support among scholars ever since the theory was seriously proposed by Bruno Stäblein (see Die Musik in Geschichte und Gegenwart, ed. F. Blume, 2:1265–1303). In general, Old-Roman chant is more ornate than Gregorian chant, but the melodic contours and formulae are too close to deny some original relationship between the two. That the Gregorian was simply derivative from the Old Roman without other influences seems impossible. It is also impossible to assert that the Old-Roman is simply an ornamented version of the Gregorian. Other solutions proposed make both chants of Roman origin, the Gregorian being the "monastic" practice that was carried northward by the monks into England and France. Such a solution does not explain the relationship between the two chants, however. The best solution still seems to be that proposed by M. Huglo and arrived at also by W. Apel, that the Old-Roman version comes closest to the Roman practice at the time of Charlemagne and that it combined with the Gallican usage to give birth during the 8th century to the version now called Gregorian. The testimony of Amalarius of Metz (early 9th century) certainly supports this view. The role of Gregory in the formation of the Old-Roman repertoire remains just as dubious. A solution to the problem, without the unexpected discovery of yet-unknown documents containing the Old-Roman version and dated before the 11th century, will have to rely on internal evidence and comparative studies not yet completed.

Repertoire. When Gregorian chant was first written down in the 9th century, the type of notation employed merely indicated the direction the melody was to take, up or down, without accurate pitch differences. Until that time the repertoire had to be retained by memory without such an aid. It is remarkable, nevertheless, that the oral tradition, written down almost simultaneously throughout the vast area of present-day France, Germany, and Italy, showed such great uniformity. The retention of this repertoire by memory must have been an ever-increasing burden to the choirmaster, and the necessity of teaching it to the monks and succeeding cantors gave added impetus to the search for a system of notation. The repertoire for Mass and Office at the beginning of the 9th century must have comprised well over 2,000 pieces. These pieces were not all different one from another, and the early cantors and chant theorists exploited such similarities in inventing didactic processes.

The Recitative and Psalmody. Since the texts for most of the liturgical services are taken from the Old and New Testaments, musical systems for their proclamation had to be devised that could be altered to suit prose texts of various lengths. Simple formulas for the Old Testament reading, the Epistle and Gospel at Mass and for the readings at Matins consisted of a single recitation pitch with variants from the pitch to indicate inner and final pauses in the texts. More solemn tones were devised for the greater solemnities. Special tones were reserved for the lamentations on Good Friday and the reading of the Passion. The tones for the orations of the Mass and the Prefaces followed the same general principles of a recitation tone with cadential figures but respected the nature of the text by having two types of inner cadences. This simple principle served also for the frequent singing of Psalms at Mass and Office, where the antithetical structure of the text was clearly outlined by the musical cadences. There is some indication that the second half of the verse was not always sung on the same pitch as the first and that the text structure was delineated more clearly by a second reciting tone.

Responsorial and Antiphonal Chants. Although Gregorian chant may have arisen out of the recitation system just described, individual pieces—at first derived almost exclusively from the Psalter—became a part of the entire system. The greatest body of these pieces are the antiphons of the Mass and Office. Their counterpart are the responsories. The antiphons may originally have been sung as a kind of refrain after two groups alternated verses of the Psalter; but this practice had disappeared before the 9th century, and the antiphons that are found in Gregorian chant are larger and more elaborate and were sung only before and after the Psalm. At Mass the Introit and Communion were sung in this fashion; at the Office the many Psalms of all the hours had antiphons to be sung with them. The tonary of Regino of Prüm (d. 915) contained 1,235 such Office antiphons. It was evident to the Carolingian cantors that these antiphons could be catalogued according to certain melodic characteristics. From this one can surmise that the preceeding oral tradition for the antiphons must have had a kind of repertoire of melodic formulae to which new texts were adapted. These formulae, it can be seen, often have a kind of psalmodic structure to them, consisting of a recitation tone with cadential figures. If such was the primitive state of the music of the antiphons, with the passing of time they tended to become independent pieces in their own right.

In origin the Responsory too consisted of a refrain sung after verses of a Psalm, but this time the verses were sung by a solo cantor. By the time Gregorian chant was written down, this form had lost much of its primitive shape, except that its soloistic nature had tended to make the responsory more elaborate, especially the psalmodic verses. At Mass the Gradual and Alleluia are responsorial in nature. The Offertory seems to have passed from being antiphonal to responsorial in character shortly before the chant repertoire was written down. Even in the responds, especially in the substructure of the elaborate verses, one can see the original psalmodic principle of reciting tone and cadential figures. At Matins the responsory follows the scripture readings as a kind of musical commentary on the Scriptures. Their original improvisational nature had been lost before the 9th century.

Other Pieces. The chant repertory included other specific pieces that were needed to complete the Mass and Office services. Some of these chants may originally have been quite simple in nature, somewhat in the style of a litany, but later developed into full-blown, ornate pieces. This had become true of the Ordinary of the Mass by the late Carolingian period. Elaborate Kyrie's, Gloria's, Sanctus's, and Agnus Dei's can be found in all Graduales and form one of the most complicated groups of the chant repertoire. Only the Ordinary and the Alleluia cycle seem to have remained areas for new compositions after the 9th century. They were the last pieces of the standard repertory to be fixed; the composition of new chant Ordinaries continued even after the high Middle Ages. All of these items were affected by the new forms of the trope and sequence.

Sources. Various claims have been made periodically by scholars that they have found fragments of musical notation that go back to the 8th century. But each of these items, such as the Orationale of Verona, when subjected to closer scrutiny, has been declared as non-musical in nature or as additions by later hands. The first verified fragments are still from the mid-9th century with the first full manuscript from the end of the century. The fragments are usually of isolated pieces that do not belong to the standard repertoire or are newly composed— evidence that these first attempts at mnemonic notation had a practical, didactic purpose. The treatise of Aurelian of Réomé (written about 850) has several passages that imply a knowledge on his part of a primitive notation. Of special interest are the paleofrankish fragments from the end of the 9th century that show a different system from that which became standard throughout the West. A treatise such as Hucbald's De institutione harmonica (written about 900) shows the growing concern on the part of cantors for a more precise notation than that of the mnemonic neumes then in use. (A list of full manuscripts from about 900 can be found in Suñol, Introduction … 32.) Not until a century later (about 1000) was the staff invented, and then it required another half century before it was perfected to the point where melodic accuracy could be perfectly ascertained. For this reason chant scholars must search for the pieces of the earlier MSS in later 11th-and 12th-century manuscripts to transcribe with accuracy. In sum, the first manuscripts containing Gregorian chant in an accurate unequivocal melodic notation came from shortly after the year 1000; the repertory can be traced back to 900 in a mnemonic notation, but only in fragments and descriptions befor that.

Theorists. In addition to the manuscripts containing the chant repertory, there exist the chant theorists, who furnish invaluable information on the repertory and how it was performed. The first such theorist is Aurelian of Réomé, who wrote his Musicá disciplina about 850. A fragment of this treatise has been erroneously attributed to Alcuin. Aurelian in the first eight chapters of his work gives a résumé of the theory of music inherited from the ancient Greeks through Boethius and Cassiodorus. He makes no attempt to reconcile this theory with the chant practice of his day. Boethius in particular was used in the Carolingian schools as the auctor itas in music. From chapters 9 to 20, however, Aurelian makes a first attempt of cataloguing the chant repertory according to the toni. For the first time he speaks of the Byzantine octoechos, or eight modes, and of the manner in which the Psalms sung in these modes are to be joined to the antiphons and responds. Subsequent chant theorists, such as Regino of Prüm (d. 915), Hucbald of St. Armand (d. 930), and Remy of Auxerre (end of 9th century), began the arduous task of trying to combine these two divergent theoretical systems and to use them for an explanation of Gregorian chant. The octoechos became identified for the first time with the eight-mode Boethian system in the treatise De alia musica (late 9th century). It is not until the 1lth century that the amalgamation is completed in the treatises of guido of arezzo, berno of reichenau, and hermannus contractus. There is evidence that the inherited Boethian theory had an effect on the chant that may have been altered at times to fit the auctoritas. Boethius continued to be taught as the authority in the schools and universities of the Middle Ages, while Guido became the infallible guide to the cantor.

Gregorian Chant Style. To the 20th-century ear, accustomed to the gigantic sounds of the orchestra of the romanticist period and the striking contrasts of dynamics and timbre inherent in the romanticist style, Gregorian chant seems unemotional and less expressive. To a listener of the Middle Ages, however, this was not true. The Gregorian style was broad in its expressive content, even though more austere than the music of recent centuries. Since it had to accommodate so many prose texts, it ranged from formulalike patterns such as psalmody and antiphon types to highly expressive melismatic passages such as the jubilus of the Alleluia. These extremes in the style have often been labeled syllabic and melismatic, or accentus and concentus. Such terms, however, are not synonymous. Syllabic chant refers to those pieces in which each syllable has predominantly one note, seldom more; melismatic chant has expressive vocalises on important syllables. In between these two lie most of the chant pieces. The Sequence, for example, is syllabic; the Alleluia is melismatic. Most of the Introits, Offertories, and Communions lie in between. Accentus refers to the recitative formulas used for orations and thereadings— the heightened speech patterns, while the concentus refers to true melody. In the latter the laws of music itself have their role.

Chant Rhythm. Perhaps no other aspect of Gregorian chant has been so feverishly debated by scholars as that of the original rhythm of the chant. The following facts are accepted by all: The earliest chant manuscripts (from c. 900) show various ways of writing the same neume and these variants imply rhythmic differences. Many of these manuscripts reinforce this notational difference with letters (called Romanian letters) to signify rhythmic alteration. Other differences in notation involve vocal phenomena (such as the liquescents and the quilisma) that also have rhythmic implications. The basic diference in interpretation of these signs among scholars centers around the length of the altered notes in relationship to a given pulse. Further dispute arises as to the rhythmic organization of the given pulse. It was in answer to this latter question that Dom mocquereau developed the theory of rhythm, usually called the Solesmes theory, in which the basic pulses are related by groups of two or three and with the unifying factor being called the ictus. This ictus is conceived as the end of rhythmic motion in its fundamental state of movement—repose. Mocquereau attempted to show at great length that this is the natural rhythm of the Latin word, which gave its rhythm to the chant. Such a theory has much merit in dealing with psalmody and other pieces belonging to the accentus group; it proves more difficult to maintain in dealing with the concentus. Here the ictus, or rhythmic subdivision, corresponds at times with the end or repose of the Latin word, at times with accent or force (as when it corresponds in larger phrases with the accent of the text), at times with length, or even at times with melodic contour. There is no doubt that Mocquereau's theory grew out of the accentualist or oratorical theory of Dom Pothier, where the textual accent of the Latin word was the organizing principle, and that he broadened the concept so that it could serve also for the melismatic passages. To introduce it into present books, an elaborate system of vertical and horizontal bars was invented.

The Solesmes theory was rejected at the turn of the 19th century by most German scholars who ranked themselves among the mensuralists, i.e., those favoring various time values with accent as the chief unifying factor. The former mensuralist theories of Dechevrens, Peter Wagner, Dom Jeannin, and Bonvin have all but been forgotten. Chief exponents of mensuralism today are E. Jammers and J. Vollaerts, although their theories admit of only two or three time values and are a kind of free rhythm with irregular occuring accents. It can be said that the weakness of the Solesmes theory lies in its historical justification in the nature of the Latin word since it presupposes that this rhythm was established for chant in the 5th and 6th centuries during its formative period, a supposition that is hard to maintain. The historical evidence in favor of the long and short time values comes chiefly from the theorists, and it seems a less forced interpretation of the early neumes and the different ways in which they are written. More recent rhythmic studies by T. Agostoni and E. Cardine are tending to a modification of the Solesmes theory that brings it closer to the interpretation of J. Vollaerts. It is unfortunate that the introduction of polyphony and the tendency to clearer pitch indications in notation saw at the same time a less accurate rhythmic care. The notation in campo aperto, i.e., without lines, and thus mnemonic in character, is less accurate in pitch but more accurate in rhythm, while the later diastematic manuscripts, i.e., with lines, are more accurate in pitch but less so in rhythm and vocal nuances.

Formal Aspects of Gregorian Chant. All patterns found in later Western music are found also in chant. Musicologists have taken great pains to find ABA and Rondo forms in various chant pieces. All of this is true but says little about the formal structures of the chant melody. Being pure melody, the chant relies on purely melodic motives for its formal structure. In general, the high point of the line is arrived at rather rapidly and tapers off gradually. The length of the line is frequently dictated by the text and its components. There is no music where the shape of the text so affects the shape of the line. Sequential structures are found but never stressed as formative elements. The general punctuation of the text determines the inner cadences, which, as a rule, do not stress the final tone. Later melodies tend to have larger leaps in succession, while the older melodies use the leap beyond a third with great discretion. The word accent does not always receive musical development but frequently is higher in pitch than the unaccented syllables. There is some evidence that interest in the Latin rhythmic cursus may have had some influence in cadential formulas, especially of the psalm tones. The manner in which a typical pattern can be altered to fit a new text shows a keen appreciation of text declamation and a freedom within a given form that is always expressive and sensitive. The subtlety was lost or obscured by the advent of polyphony.

The Modal System. The chief unifying element in Gregorian chant is its modal structure. The oral tradition from which chant arose was undoubtedly one of a group of melodic formulae or phrases that could be adapted to various texts. These formulae were traditionally grouped into eight divisions depending on the melodic contour, the manner of beginning, and the relationship between the reciting or dominant tone and the ending formula. There is reason to believe that originally the beginning was most important in such a grouping, but certainly after the influence of the classical Greek theories inherited through Boethius the ending or final note and its relationship to the reciting or dominant note proved the vital factor in determining mode. Also from Boethius is derived the influence of range as an important element. The Byzantine theory that was inherited spoke of four authentic modes and four plagal or derivative modes. A plagal mode shared with its respective authentic mode the same final but usually had a lower dominant or reciting tone, thus throwing the whole range somewhat lower. In the authentic modes the final or cadential figure comes at the bottom of the range; in the plagal modes, it is in the middle. The accompanying table presents the standard modal theory as it was fully developed in the treatises of the 11th century. This theory cannot be applied rigidly to all chants. By the introduction of the B^b the general flavor of a mode can be altered and transpositions can be effected. There are no other accidentals possible in chant, and thus chromaticism is impossible. The tritone (interval of the augmented fourth) was avoided also in later chant, although the treatise of Hucbald De institutione harmonica cites this interval without prejudice and gives examples of it. Later tonaries give model modal melodies that embody the characteristics of each mode and served didactic purposes, but the repertory itself is much freer in its adherence to modal structure. Some of the more elaborate verses of the soloistic responsories use both the plagal and authentic ranges of the same mode and thus exploit all of the melodic possibilities of the mode.

Subsequent History of Gregorian Chant. After the Carolingian period the interests of the chant composer turned to tropes and Sequences and the rise of polyphony. The standard repertory remained in use, but it lost its rhythmic piquancy and became the source for polyphonic treatment. Several new Offices were written that exploited the modal theories by presenting the antiphons of the night Office in modal succession, but general interest in chant composition waned.

The Council of Trent. By the 16th century the condition of chant was truly lamentable, and a reform was badly needed. Unfortunately the Medicean edition that resulted from an attempt at reform (see chant books, printed editions of) was not founded on scholarly principles and reflected more the aesthetics of the late Renaissance than the early Middle Ages. This edition, however, remained the source for all subsequent editions until the 19th century. Pioneers in musical research in the 19th century, such as Lambillotte, La Fage, D'Ortigue, and Nasard, laid the basis for the subsequent more accurate work of the Solesmes school. To this latter, under the directorship of Dom Pothier and Dom Mocquereau, belongs the lasting credit of making available the original mnemonic manuscripts in facsimile editions in the series Paléographie musicale grégorienne and of initiating a series of monographs that made scholars search out the original documents. The treatises of the theorists were gathered together by M. gerbert and E. Coussemaker. The controversies that arose in opposition to the Solesmes theories, with P. Wagner and F. Gevaert as chief protagonists, gave rise to intensive chant studies that are still accurate sources for information.

Present Practice. As a result of chant scholarship since the mid-19th century, the present practice can be said to come closer to the original in its melodic precision than that of any previous century. However, the rhythmic controversies still continue; there are more performances in the mensuralist style, and there is less adherence to the Solesmes school. Frequently the chant is accompanied on the organ, which thus adds a third dimension never intended by the original composers. Often this accompaniment totally falsifies the underlying modal structure. True chant must be unaccompanied. Attempts at congregational use of the chant repertory in the 20th century have been limited to the simple Mass Ordinaries and have not been universally successful. It is generally found to be too alien to 20th-century aesthetic tastes. Various systems of arm and hand motions also have been invented to direct chant (called chironomy) and have been most successfully used. With the increase of the vernacular in the liturgy, less interest has been shown in Gregorian chant, although many attempts at adapting its melodies to new English texts have been made.

Bibliography: A complete bibliography of Gregorian chant to 1935 can be found in g. m. suÑol, Introduction à la paléographie musicale grégorienne (Tournai 1935), and an extension of the same Bibliographie grégorienne, 1935–1937 (3d ed. Solesmes-Rome 1958). A further extensive bibliography is found in b. stÄblein, "Choral," Die Musik in Geschichte und Gegenwart, ed. f. blume (Kassel-Basel 1949–) 2:1265–1303. The two most extensive works on Gregorian chant are p. wagner, Einführung in die gregorianischen Melodien, 3 v. (Leipzig), v.1 (3d ed. 1911), v.2 (2d ed. 1912), v.3 (1921); repr. (Hildesheim 1962) and w. apel, Gregorian Chant (Bloomington, Indiana 1958). The following works in English are comprehensive and useful: g. reese, Music in the Middle Ages (New York 1940). j. smits van waesberghe, Gregorian Chant (London 1949). h. anglÈs, "Latin Chant before St. Gregory" and "Gregorian Chant," New Oxford History of Music, ed. j. a. westrup, 11 v. (New York 1957–) 2:58–127. Indispensable sources are: m. gerbert, Scriptores ecclesiastici de musica sacra potissimum, 3 v. (Milan 1931). h. coussemaker, Scriptorum de musica medii aevi nova series, 4 v. (Paris 1864–76). Paléographie musicale (Solesmes 1889–). h. m. bannister, Monument Vaticani di paleografia musicale latina, 2 v. (Leipzig 1913). Selective list of other important works follows. r. j. hesbert, ed., Antiphonale missarum sextuplex (Brussels 1935). w. h. frere, ed., Antiphonale Sarisburiense (London 1901–26); Graduale Sarisburiense (London 1894); The Winchester Troper (London 1894). p. m. ferretti, Esthétique grégorienne (Paris 1938). a. gastouÉ, L'Antiphonaire grégorien (Paris 1907); Le Graduel et l'antiphonaire (Paris 1913); Les Origines du chant romain (Paris 1907). f. a. gevaert, La Mélopée antique dans le chant de l'Église latine (Ghent 1895); Les Origines du chant liturgique de l'Église latine (Ghent 1890). a. mocquereau, Le Nombre musical grégorien, 2 v. (Tournai 1908–27). j. pothier, Les Mélodies grégoriennes (Tournai 1880). p. wagner, Einführung in die gregorianischen Melodien, 3 v. (Leipzig), v.1 (3d ed. 1911), v.2 (2d ed. 1912), v.3 (1921); repr. (Hildesheim 1962). o. ursprung, Die katholische Kirchenmusik (Potsdam 1931). r. van doren, Étude sur l'influence musicale de l'Abbaye de Saint-Gall, VIII ^e au XI ^e siècle (Brussels 1925). f. tack, Gregorian Chant (Cologne 1960). l. agustoni, Gregorianischer Choral (Freiburg 1963). Études grégoriennes, 5 v. (Solesmes 1954–62). w. apel, Gregorian Chant (Bloomington, Indiana 1958). h. hucke, "Toward a New Historical View of Gregorian Chant," Journal of the American Musicological Society 33 (1980) 411–87. h. van der werf, The Emergence of Gregorian Chant (Rochester, New York 1983). d. hughes, "Evidence for the Traditional View of the Transmission of Gregorian Chant," Journal of the American Musicological Society 40 (1987) 377–404. k. levy, "Charlemagne's Archetype of Gregorian Chant," Journal of the American Musicological Society 40 (1987) 1–30. j. mckinnon, "The Emergence of Gregorian Chant in the Carolingian Era," Antiquity and the Middle Ages (London 1990) 88–119. d. hiley, Western Plainchant: A Handbook (Oxford 1993).

[r. g. weakland/eds.]

Plainsong or Plainchant. The traditional music of the Latin Christian rite. It is generally known as ‘Gregorian’ chant, though its exact connection with St Gregory the Great is debated.

Gre·go·ri·an chant • n. church music sung as a single vocal line in free rhythm and a restricted scale (plainsong), in a style developed for the medieval Latin liturgy.

Gregorian Chant. Solo and unison plainsong choral chants assoc. with Pope Gregory I which became the fundamental mus. of the RC Church. See Plainsong.

Gregorian Chant: see GREGORY I.