Gregorian chant is the central tradition of Western plainchant, a form of monophonic liturgical music within Western Orthodoxy that accompanied the celebration of Mass and other ritual services. It is named after Pope Gregory I, Bishop of Rome from 590 to 604, who is traditionally credited for having ordered the simplification and cataloging of music assigned to specific celebrations in the church calendar. The resulting body of music is the first to be notated in a system ancestral to modern musical notation. In general, the chants were learned by the viva voce method, that is, by following the given example orally, which took many years of experience in the Schola Cantorum. Gregorian chant originated in monastic life, in which celebrating the 'Divine Office' eight times a day at the proper hours was upheld according to the Rule of St. Benedict. Singing psalms made up a large part of the life in a monastic community, while a smaller group and soloists sang the chants. In its long history, Gregorian chant has been subjected to many gradual changes and some reforms.
Gregorian chant was organized, codified, and notated mainly in the Frankish lands of western and central Europe during the 10th to 13th centuries, with later additions and redactions, but the texts and many of the melodies have antecedents going back several centuries earlier. Although popular belief credited Pope Gregory the Great with having personally invented Gregorian chant (in much the same way that a biblical prophet would transmit a divinely received message), scholars now believe that the chant bearing his name arose from a later Carolingian synthesis of Roman and Gallican chant, and that at that time the attribution to Gregory I was a "marketing ruse" to invest it with a sanctified pedigree, as part of an effort to create one liturgical protocol that would be practised throughout the entire Holy Roman Empire.
Gregorian chants are organized into eight modes (scales). Typical melodic features include characteristic incipits and cadences, the use of reciting tones around which the other notes of the melody revolve, and a vocabulary of musical motifs woven together through a process called centonization to create families of related chants.
Although the modern eight-tone major and minor scales are strongly related to two of these church modes (the Ionian and Aeolian, respectively), they function according to different harmonic rules. The church modes are based on six-note patterns called hexachords, the main notes of which are called the dominant and the final. Depending on where the final falls in the sequence of the hexachord, the mode is characterized as either authentic or plagal. Modes with the same final share certain characteristics, and it is easy to modulate back and forth between them; hence, the eight modes fall into four larger groupings based on their finals.
The oldest manuscripts of Gregorian chants were written using a graphic notation which uses a repertoire of specific signs called neumes; each neume designates a basic musical gesture (see musical notation). As books, made of vellum (prepared sheepskins), were very expensive, the text was abbreviated wherever possible, with the neumes written over the text. This was a notation without lines and no exact melodic contour could be deciphered from it, which implies that the repertoire was learnt by rote. In later stadia, the neumes are written onto staves of one or more lines; by the 11th century this had evolved into square notation, from which eventually the modern five-line staff developed in the 16th century. As the dominating musical tradition throughout Europe, Gregorian chant became the root of all subsequent musical developments in Western music, beginning with the rise of polyphony in the 11th century.
Gregorian chant was traditionally sung by choirs of men and boys in churches, or by monastics in their chapels, and is commonly heard in celebrations of the Western RiteLiturgies. It is the music of the Roman Rite, performed in the Mass and the monastic Office.
Development of earlier plainchant
Singing has been part of the Christian liturgy since the earliest days of the Church. Until the mid-1990s, it was widely accepted that the psalmody of ancient Jewish worship significantly influenced and contributed to early Christian ritual and chant. This view is no longer generally accepted by scholars, due to analysis that shows that most early Christian hymns did not have Psalms for texts, and that the Psalms were not sung in synagogues for centuries after the Destruction of the Second Temple in AD 70. However, early Christian rites did incorporate elements of Jewish worship that survived in later chant tradition. Canonical hours have their roots in Jewish prayer hours. "Amen" and "alleluia" come from Hebrew, and the threefold "sanctus" derives from the threefold "kadosh" of the Kedusha.
The New Testament mentions singing hymns during the Last Supper: "When they had sung the hymn, they went out to the Mount of Olives" Template:Bibleverse. Other ancient witnesses such as Pope Clement I, Tertullian, St. Athanasius, and Egeria confirm the practice, although in poetic or obscure ways that shed little light on how music sounded during this period. The 3rd-century Greek "Oxyrhynchus hymn" survived with musical notation, but the connection between this hymn and the plainchant tradition is uncertain.
Musical elements that would later be used in the Roman Rite began to appear in the 3rd century. The Apostolic Tradition, attributed to the theologian Hippolytus, attests the singing of Hallel psalms with Alleluia as the refrain in early Christian agape feasts. Chants of the Office, sung during the canonical hours, have their roots in the early 4th century, when desert monks following St. Anthony introduced the practice of continuous psalmody, singing the complete cycle of 150 psalms each week. Around 375, antiphonal psalmody became popular in the Christian East; in 386, St. Ambrose introduced this practice to the West.
Scholars are still debating how plainchant developed during the 5th through the 9th centuries, as information from this period is scarce. Around 410, St. Augustine described the responsorial singing of a Gradual psalm at Mass. At ca. 520, Benedictus of Nursia established what is called the rule of St. Benedict, in which the protocol of the Divine Office for monastic use was laid down. Around 678, Roman chant was taught at York. Distinctive regional traditions of Western plainchant arose during this period, notably in the British Isles (Celtic chant), Spain (Mozarabic), Gaul (Gallican), and Italy (Old Roman, Ambrosian and Beneventan). These traditions may have evolved from a hypothetical year-round repertory of 5th-century plainchant after the western Roman Empire collapsed.
Origins of the new traditionRoman Rite. According to James McKinnon, the core liturgy of the Roman Mass was compiled over a brief period in the 8th century in a project overseen by Chrodegang of Metz. Other scholars, including Andreas Pfisterer and Peter Jeffery, have argued for an earlier origin for the oldest layers of the repertory.
Scholars debate whether the essentials of the melodies originated in Rome, before the 7th century, or in Francia, in the 8th and early 9th centuries. Traditionalists point to evidence supporting an important role for Pope Gregory the Great between 590 and 604, such as that presented in Heinrich Bewerunge's article in the Catholic Encyclopedia. Scholarly consensus, supported by Willi Apel and Robert Snow, asserts instead that Gregorian chant developed around 750 from a synthesis of Roman and Gallican chant commissioned by Carolingian rulers in France. During a visit to Gaul in 752–753, Pope Stephen II had celebrated Mass using Roman chant. According to Charlemagne, his father Pepin abolished the local Gallican rites in favor of the Roman use, in order to strengthen ties with Rome. In 785–786, at Charlemagne's request, Pope Hadrian I sent a papal sacramentary with Roman chants to the Carolingian court. This Roman chant was subsequently modified, influenced by local styles and Gallican chant, and later adapted into the system of eight modes. This Frankish-Roman Carolingian chant, augmented with new chants to complete the liturgical year, became known as "Gregorian." Originally the chant was probably so named to honor the contemporary Pope Gregory II, but later lore attributed the authorship of chant to his more famous predecessor Gregory the Great. Gregory was portrayed dictating plainchant inspired by a dove representing the Holy Spirit, giving Gregorian chant the stamp of holy authority. Gregory's authorship is popularly accepted as fact to this day.
Dissemination and hegemony
Gregorian chant appeared in a remarkably uniform state across Europe within a short time. Charlemagne, once elevated to Holy Roman Emperor, aggressively spread Gregorian chant throughout his empire to consolidate religious and secular power, requiring the clergy to use the new repertory on pain of death. From English and German sources, Gregorian chant spread north to Scandinavia, Iceland and Finland. In 885, Pope Stephen V banned the Slavonic liturgy, leading to the ascendancy of Gregorian chant in Eastern Catholic lands including Poland, Moravia, Slovakia, and Austria.
The other plainchant repertories of the Christian West faced severe competition from the new Gregorian chant. Charlemagne continued his father's policy of favoring the Roman Rite over the local Gallican traditions. By the 9th century the Gallican rite and chant had effectively been eliminated, although not without local resistance. The Gregorian chant of the Sarum Rite displaced Celtic chant. Gregorian coexisted with Beneventan chant for over a century before Beneventan chant was abolished by papal decree (1058). Mozarabic chant survived the influx of the Visigoths and Moors, but not the Roman-backed prelates newly installed in Spain during the Reconquista. Restricted to a handful of dedicated chapels, modern Mozarabic chant is highly Gregorianized and bears no musical resemblance to its original form. Ambrosian chant alone survived to the present day, preserved in Milan due to the musical reputation and ecclesiastical authority of St. Ambrose.
Gregorian chant eventually replaced the local chant tradition of Rome itself, which is now known as Old Roman chant. In the 10th century, virtually no musical manuscripts were being notated in Italy. Instead, Roman Popes imported Gregorian chant from the German Holy Roman Emperors during the 10th and 11th centuries. For example, the Credo was added to the Roman Rite at the behest of the German emperor Henry II in 1014. Reinforced by the legend of Pope Gregory, Gregorian chant was taken to be the authentic, original chant of Rome, a misconception that continues to this day. By the 12th and 13th centuries, Gregorian chant had supplanted or marginalized all the other Western plainchant traditions.
Later sources of these other chant traditions show an increasing Gregorian influence, such as occasional efforts to categorize their chants into the Gregorian modes. Similarly, the Gregorian repertory incorporated elements of these lost plainchant traditions, which can be identified by careful stylistic and historical analysis. For example, the Improperia of Good Friday are believed to be a remnant of the Gallican repertory.
Early sources and later revisions
The first extant sources with musical notation were written around 930 (Graduale Laon). Before this, plainchant had been transmitted orally. Most scholars of Gregorian chant agree that the development of music notation assisted the dissemination of chant across Europe. The earlier notated manuscripts are primarily from Regensburg in Germany, St. Gall in Switzerland, Laon and St. Martial in France.
Gregorian chant has in its long history been subjected to a series of redactions to bring it up to changing contemporary tastes and practice. The more recent redaction undertaken in the Benedictine Abbey of St. Pierre, Solesmes, has turned into a huge undertaking to restore the allegedly corrupted chant to a hypothetical "original" state. Early Gregorian chant was revised to conform to the theoretical structure of the modes. In 1562–63, the Council of Trent banned most sequences. Guidette's Directorium chori, published in 1582, and the Editio medicea, published in 1614, drastically revised what was perceived as corrupt and flawed "barbarism" by making the chants conform to contemporary aesthetic standards. In 1811, the French musicologist Alexandre-Étienne Choron, as part of a conservative backlash following the liberal Catholic orders' inefficacy during the French Revolution, called for returning to the "purer" Gregorian chant of Rome over French corruptions.
In the late 19th century, early liturgical and musical manuscripts were unearthed and edited. Earlier, Dom Prosper Gueranger revived the monastic tradition in Solesmes. Re-establishing the Divine Office was among his priorities, but no proper chantbooks existed. Many monks were sent out to libraries throughout Europe to find relevant Chant manuscripts. In 1871, however, the old Medicea edition was reprinted (Pustet, Regensburg) which Pope Pius IX declared the only official version. In their firm belief that they were on the right way, Solesmes increased its efforts. In 1889, after decades of research, the monks of Solesmes released the first book in a planned series, the Paléographie Musicale. The incentive of its publication was to demonstrate the corruption of the 'Medicea' by presenting photographed notations originating from a great variety of manuscripts of one single chant, which Solesmes called forth as witnesses to assert their own reforms.
The monks of Solesmes brought in their heaviest artillery in this battle, as indeed the academically sound 'Paleo' was intended to be a war-tank, meant to abolish once and for all the corrupted Pustet edition. On the evidence of congruence throughout various manuscripts (which were duely published in facsimile editions with ample editorial introductions) Solesmes was able to work out a practical reconstruction. This reconstructed chant was academically praised, but rejected by Rome until 1903, when Pope Leo XIII died. His successor, Pope Pius X, promptly accepted the Solesmes chant — now compiled as the Liber usualis — as authoritative. In 1904, the Vatican edition of the Solesmes chant was commissioned. Serious academic debates arose, primarily owing to stylistic liberties taken by the Solesmes editors to impose their controversial interpretation of rhythm. The Solesmes editions insert phrasing marks and note-lengthening episema and mora marks not found in the original sources.
Conversely, they omit significative letters found in the original sources, which give instructions for rhythm and articulation such as speeding up or slowing down. These editorial practices has placed the historical authenticity of the Solesmes interpretation in doubt. Ever since the restoration of Chant was taken up in Solesmes, there have been lengthy discussions of exactly what course was to be taken. Some favored a strict academic rigour and wanted to postpone publications, while others concentrated on practical matters and wanted to supplant the corrupted tradition as soon as possible. Roughly a century later, there still exists a breach between a strict musicological approach and the practical needs of church choirs. Thus the established performance tradition since the onset of the restoration is at odds with musicological evidence.
In his motu proprio Tra le sollecitudini, Pius X mandated the use of Gregorian chant, encouraging the faithful to sing the Ordinary of the Mass, although he reserved the singing of the Propers for males. While this custom is maintained in traditionalist Catholic communities, the Catholic Church no longer persists with this ban. Vatican II officially allowed worshipers to substitute other music, particularly sacred polyphony, in place of Gregorian chant, although it did reaffirm that Gregorian chant was still the official music of the Catholic Church, and the music most suitable for worship.
Gregorian chant is, of course, vocal music. The text, the phrases, words and eventually the syllables, can be sung in various ways. The most straightforward is recitation on the same tone, which is called "syllabic" as each syllable is sung to a single tone. Likewise, simple chants are often syllabic throughout with only a few instances where two or more notes are sung on one syllable. "Neumatic" chants are more embellished and ligatures, a connected group of notes, written as a single compound neume, abound in the text. Melismatic chants are the most ornate chants in which elaborate melodies are sung on long sustained vowels as in the Alleluia, ranging from five or six notes per syllable to over sixty in the more prolix melismas.
Gregorian chants fall into two broad categories of melody: recitatives and free melodies. The simplest kind of melody is the liturgical recitative. Recitative melodies are dominated by a single pitch, called the reciting tone. Other pitches appear in melodic formulae for incipits, partial cadences, and full cadences. These chants are primarily syllabic. For example, the Collect for Easter consists of 127 syllables sung to 131 pitches, with 108 of these pitches being the reciting note A and the other 23 pitches flexing down to G. Liturgical recitatives are commonly found in the accentus chants of the liturgy, such as the intonations of the Collect, Epistle, and Gospel during the Mass, and in the direct psalmody of the Office.Template:Listen
Psalmodic chants, which intone psalms, include both recitatives and free melodies. Psalmodic chants include direct psalmody, antiphonal chants, and responsorial chants. In direct psalmody, psalm verses are sung without refrains to simple, formulaic tones. Most psalmodic chants are antiphonal and responsorial, sung to free melodies of varying complexity.
Antiphonal chants such as the Introit, and Communion originally referred to chants in which two choirs sang in alternation, one choir singing verses of a psalm, the other singing a refrain called an antiphon. Over time, the verses were reduced in number, usually to just one psalm verse and the Doxology, or even omitted entirely. Antiphonal chants reflect their ancient origins as elaborate recitatives through the reciting tones in their melodies. Ordinary chants, such as the Kyrie and Gloria, are not considered antiphonal chants, although they are often performed in antiphonal style.Template:Listen
Responsorial chants such as the Gradual, Alleluia, Offertory, and the Office Responsories originally consisted of a refrain called a respond sung by a choir, alternating with psalm verses sung by a soloist. Responsorial chants are often composed of an amalgamation of various stock musical phrases, pieced together in a practice called centonization. Tracts are melismatic settings of psalm verses and use frequent recurring cadences and they are strongly centonized. Template:Listen
Gregorian chant evolved to fulfill various functions in the Roman Catholic liturgy. Broadly speaking, liturgical recitatives are used for texts intoned by deacons or priests. Antiphonal chants accompany liturgical actions: the entrance of the officiant, the collection of offerings, and the distribution of sanctified bread and wine. Responsorial chants expand on readings and lessons.
The non-psalmodic chants, including the Ordinary of the Mass, sequences, and hymns, were originally intended for congregational singing. The structure of their texts largely defines their musical style. In sequences, the same melodic phrase is repeated in each couplet. The strophic texts of hymns use the same syllabic melody for each stanza.
Template:Main Early plainchant, like much of Western music, is believed to have been distinguished by the use of the diatonic scale. Modal theory, which postdates the composition of the core chant repertory, arises from a synthesis of two very different traditions: the speculative tradition of numerical ratios and species inherited from ancient Greece and a second tradition rooted in the practical art of cantus. The earliest writings that deal with both theory and practice include the Enchiriadis group of treatises, which circulated in the late ninth century and possibly have their roots in an earlier, oral tradition. In contrast to the ancient Greek system of tetrachords (a collection of four continuous notes) that descend by two tones and a semitone, the Enchiriadis writings base their tone-system on a tetrachord that corresponds to the four finals of chant, D, E, F, and G. The disjunct tetrachords in the Enchiriadis system have been the subject of much speculation, because they do not correspond to the diatonic framework that became the standard Medieval scale (for example, there is a high F#, a note not recognized by later Medieval writers). A diatonic scale with a chromatically alterable b/b-flat was first described by Hucbald, who adopted the tetrachord of the finals (D, E, F, G) and constructed the rest of the system following the model of the Greek Greater and Lesser Perfect Systems. These were the first steps in forging a theoretical tradition that corresponded to chant.
Around 1025, Guido d'Arezzo revolutionized Western music with the development of the gamut, in which pitches in the singing range were organized into overlapping hexachords. Hexachords could be built on C (the natural hexachord, C-D-E^F-G-A), F (the soft hexachord, using a B-flat, F-G-A^Bb-C-D), or G (the hard hexachord, using a B-natural, G-A-B^C-D-E). The B-flat was an integral part of the system of hexachords rather than an accidental. The use of notes outside of this collection was described as musica ficta.
Gregorian chant was categorized into eight modes, influenced by the eightfold division of Byzantine chants called the oktoechos. Each mode is distinguished by its final, dominant, and ambitus. The final is the ending note, which is usually an important note in the overall structure of the melody. The dominant is a secondary pitch that usually serves as a reciting tone in the melody. Ambitus refers to the range of pitches used in the melody. Melodies whose final is in the middle of the ambitus, or which have only a limited ambitus, are categorized as plagal, while melodies whose final is in the lower end of the ambitus and have a range of over five or six notes are categorized as authentic. Although corresponding plagal and authentic modes have the same final, they have different dominants. The existent pseudo-Greek names of the modes, rarely used in medieval times, derive from a misunderstanding of the Ancient Greek modes; the prefix "Hypo-" (under, Gr.) indicates a plagal mode, where the melody moves below the final. In contemporary Latin manuscripts the modes are simply called Protus authentus /plagalis, Deuterus, Tritus and Tetrardus: the 1st mode, authentic or plagal, the 2nd mode etc. In the Roman Chantbooks the modes are indicated by Roman numerals.
- Modes 1 and 2 are the authentic and plagal modes ending on D, sometimes called Dorian and Hypodorian.
- Modes 3 and 4 are the authentic and plagal modes ending on E, sometimes called Phrygian and Hypophrygian.
- Modes 5 and 6 are the authentic and plagal modes ending on F, sometimes called Lydian and Hypolydian.
- Modes 7 and 8 are the authentic and plagal modes ending on G, sometimes called Mixolydian and Hypomixolydian.
Although the modes with melodies ending on A, B, and C are sometimes referred to as Aeolian, Locrian, and Ionian, these are not considered distinct modes and are treated as transpositions of whichever mode uses the same set of hexachords. The actual pitch of the Gregorian chant is not fixed, so the piece can be sung in whichever range is most comfortable.
Certain classes of Gregorian chant have a separate musical formula for each mode, allowing one section of the chant to transition smoothly into the next section, such as the psalm tones between antiphons and psalm verses.
Not every Gregorian chant fits neatly into Guido's hexachords or into the system of eight modes. For example, there are chants — especially from German sources — whose neumes suggest a warbling of pitches between the notes E and F, outside the hexachord system. Early Gregorian chant, like Ambrosian and Old Roman chant, whose melodies are most closely related to Gregorian, did not use the modal system. The great need for a system of organizing chants lies in the need to link antiphons with standard tones, as in for example, the psalmody at the Office. Using Psalm Tone i with an antiphon in Mode 1 makes for a smooth transition between the end of the antiphon and the intonation of the tone, and the ending of the tone can then be chosen to provide a smooth transition back to the antiphon. As the modal system gained acceptance, Gregorian chants were edited to conform to the modes, especially during 12th-century Cistercian reforms. Finals were altered, melodic ranges reduced, melismas trimmed, B-flats eliminated, and repeated words removed. Despite these attempts to impose modal consistency, some chants — notably Communions — defy simple modal assignment. For example, in four medieval manuscripts, the Communion Circuibo was transcribed using a different mode in each.
Several features besides modality contribute to the musical idiom of Gregorian chant, giving it a distinctive musical flavor. Melodic motion is primarily stepwise. Skips of a third are common, and larger skips far more common than in other plainchant repertories such as Ambrosian chant or Beneventan chant. Gregorian melodies are more likely to traverse a seventh than a full octave, so that melodies rarely travel from D up to the D an octave higher, but often travel from D to the C a seventh higher, using such patterns as D-F-G-A-C. Gregorian melodies often explore chains of pitches, such as F-A-C, around which the other notes of the chant gravitate. Within each mode, certain incipits and cadences are preferred, which the modal theory alone does not explain. Chants often display complex internal structures that combine and repeat musical subphrases. This occurs notably in the Offertories; in chants with shorter, repeating texts such as the Kyrie and Agnus Dei; and in longer chants with clear textual divisions such as the Great Responsories, the Gloria, and the Credo.
Chants sometimes fall into melodically related groups. The musical phrases centonized to create Graduals and Tracts follow a musical "grammar" of sorts. Certain phrases are used only at the beginnings of chants, or only at the end, or only in certain combinations, creating musical families of chants such as the Iustus ut palma family of Graduals. Several Introits in mode 3, including Loquetur Dominus above, exhibit melodic similarities. Mode III (E authentic) chants have C as a dominant, so C is the expected reciting tone. These mode III Introits, however, use both G and C as reciting tones, and often begin with a decorated leap from G to C to establish this tonality. Similar examples exist throughout the repertory.
The earliest notated sources of Gregorian chant (written ca. 950) used symbols called neumes (Gr. sign (of the hand) to indicate tone-movements and relative duration within each syllable. A sort of musical stenography that seems to focus on gestures and tone-movements but not the specific pitches of individual notes, nor the relative starting pitches of each neume. Given the fact that Chant was learned in an oral tradition in which the texts and melodies were sung from memory, this was obviously not necessary. The neumatic manuscripts display great sophistication and precision in notation and a wealth of graphic signs to indicate the musical gesture and proper pronunciation of the text. Scholars postulate that this practice may have been derived from cheironomic hand-gestures, the ekphonetic notation of Byzantine chant, punctuation marks, or diacritical accents. Later adaptations and innovations included the use of a dry-scratched line or an inked line or two lines, marked C or F showing the relative pitches between neumes. Consistent relative heightening first developed in the Aquitaine region, particularly at St. Martial de Limoges, in the first half of the eleventh century. Many German-speaking areas, however, continued to use unpitched neumes into the twelfth century. Additional symbols developed, such as the custos, placed at the end of a system to show the next pitch. Other symbols indicated changes in articulation, duration, or tempo, such as a letter "t" to indicate a tenuto. Another form of early notation used a system of letters corresponding to different pitches, much as Shaker music is notated.Dom. E. Cardine (see below under 'rhythm'), ornamental neumes have received more attention from both researchers and performers. B-flat is indicated by a "b-mollum" (Lat. soft), a rounded undercaste 'b' placed to the left of the entire neume in which the note occurs, as shown in the "Kyrie" to the right. When necessary, a "b-durum" (Lat. hard), written squarely, indicates B-natural and serves to cancel the b-mollum . This system of square notation is standard in modern chantbooks.
- Development of notation styles is discussed at Dolmetsch online, accessed 4 July 2006
- David Hiley, Western Plainchant pp. 484–5.
- Willi Apel, Gregorian Chant p. 34.
- Apel, Gregorian Chant p. 74.
- Hiley, Western Plainchant pp. 484–7 and James McKinnon, Antiquity and the Middle Ages p. 72.
- McKinnon, James W.: "Christian Church, music of the early", Grove Music Online ed. L. Macy (Accessed 11 July 2006), (subscription access)
- Hiley, Western Plainchant p. 486.
- James McKinnon, Antiquity and the Middle Ages p. 320.
- Template:Ws, article by Heinrich Bewerunge.
- Apel, Gregorian Chant p. 79.
- McKinnon, Antiquity and the Middle Ages p. 114.
- Wilson, Music of the Middle Ages p. 13.
- David Wilson, Music of the Middle Ages p. 10.
- Hiley, Western Plainchant p. 604.
- Apel, Gregorian Chant p. 80.
- Richard Hoppin, Medieval Music p. 47.
- Carl Parrish, "A Treasury of Early Music" pp. 8–9
- Apel, Gregorian Chant pp. 288–289.
- Hiley, Western Plainchant p. 622.
- Hiley, Western Plainchant p. 624–627.
- Template:Cite web
- Hoppin, Medieval Music pp. 85–88.
- Apel, Gregorian Chant p. 203
- Hoppin, Anthology of Medieval Music p. 11.
- Hoppin, Medieval Music p. 81.
- Hoppin, Medieval Music p. 123.
- Hoppin, Medieval Music p. 131.
- Wilson, Music of the Middle Ages p. 11.
- Hoppin, Medieval Music pp. 64–5.
- Hoppin, Medieval Music p. 82.
- Wilson, Music of the Middle Ages p. 22.
- Apel, Gregorian Chant p. 166–78, and Hiley, Western Plainchant p. 454.
- Hiley, Western Plainchant pp. 608–10.
- Apel, Gregorian Chant pp. 171–2.
- Apel, Gregorian Chant pp. 256–7.
- Wilson, Music of the Middle Ages p. 21.
- Apel, Gregorian Chant pp. 258–9.
- Apel, Gregorian Chant pp. 344–63.
- Hiley, Western Plainchant pp. 110–113.
- Levy, Kenneth: "Plainchant", Grove Music Online, ed. L. Macy (Accessed 20 January 2006), (subscription access)