Medieval Music - Overview - Theory and Notation - Music Theory

Music Theory

The music theory of the Mediaeval period saw several advances over previous practice both in regard to tonal material, texture, and rhythm. Concerning rhythm, this period had several dramatic changes in both its conception and notation. During the early Mediaeval period there was no method to notate rhythm, and thus the rhythmical practice of this early music is subject to heated debate among scholars. The first kind of written rhythmic system developed during the 13th century and was based on a series of modes. This rhythmic plan was codified by the music theorist Johannes de Garlandia, author of the De Mensurabili Musica (c.1250), the treatise which defined and most completely elucidated these rhythmic modes. In his treatise Johannes de Garlandia describes six species of mode, or six different ways in which longs and breves can be arranged. Each mode establishes a rhythmic pattern in beats (or tempora) within a common unit of three tempora (a perfectio) that is repeated again and again. Furthermore, notation without text is based on chains of ligatures (the characteristic notations by which groups of notes are bound to on another). The rhythmic mode can generally be determined by the patterns of ligatures used. Once a rhythmic mode had been assigned to a melodic line, there was generally little deviation from that mode, although rhythmic adjustments could be indicated by changes in the expected pattern of ligatures, even to the extent of changing to another rhythmic mode. The next step forward concerning rhythm came from the German theorist Franco of Cologne. In his treatise Ars cantus mensurabilis ("The Art of Mensurable Music"), written around 1280, he describes a system of notation in which differently shaped notes have entirely different rhythmic values. This is a striking change from the earlier system of de Garlandia. Whereas before the length of the individual note could only be gathered from the mode itself, this new inverted relationship made the mode dependent upon—and determined by—the individual notes or figurae that have incontrovertible durational values, an innovation which had a massive impact on the subsequent history of European music. Most of the surviving notated music of the 13th century uses the rhythmic modes as defined by Garlandia. The step in the evolution of rhythm came after the turn of the 13th century with the development of the Ars Nova style.

The theorist who is most well recognized in regard to this new style is Philippe de Vitry, famous for writing the Ars Nova ("New Art") treatise around 1320. This treatise on music gave its name to the style of this entire era. In some ways the modern system of rhythmic notation began with Vitry, who completely broke free from the older idea of the rhythmic modes. The notational predecessors of modern time meters also originate in the Ars Nova. This new style was clearly built upon the work of Franco of Cologne. In Franco's system, the relationship between a breve and a semibreves (that is, half breves) was equivalent to that between a breve and a long: and, since for him modus was always perfect (grouped in threes), the tempus or beat was also inherently perfect and therefore contained three semibreves. Sometimes the context of the mode would require a group of only two semibreves, however, these two semibreves would always be one of normal length and one of double length, thereby taking the same space of time, and thus preserving the perfect subdivision of the tempus. This ternary division held for all note values. In contrast, the Ars Nova period introduced two important changes: the first was an even smaller subdivision of notes (semibreves, could now be divided into minim), and the second was the development of "mensuration." Mensurations could be combined in various manners to produce metrical groupings. These groupings of mensurations are the precursors of simple and compound meter. By the time of Ars Nova, the perfect division of the tempus was not the only option as duple divisions became more accepted. For Vitry the breve could be divided, for an entire composition, or section of one, into groups of two or three smaller semibreves. This way, the tempus (the term that came to denote the division of the breve) could be either "perfect," (Tempus perfectus) with ternary subdivision, or "imperfect,"(Tempus imperfectus) with binary subdivision. In a similar fashion, the semibreve's division (termed prolation) could be divided into three minima (prolatio perfectus or major prolation) or two minima (prolatio imperfectus or minor prolation) and, at the higher level, the longs division (called modus) could be three or two breves (modus perfectus or perfect mode, or modus imperfectus or imperfect mode respectively). Vitry took this a step further by indicating the proper division of a given piece at the beginning through the use of a "mensuration sign," equivalent to our modern "time signature. Tempus perfectus was indicated by a circle, while tempus imperfectus was denoted by a half-circle (our current "C" as a stand-in for the 4/4 time signature is actually a holdover from this practice, not an abbreviation for "common time", as popularly believed). While many of these innovations are ascribed to Vitry, and somewhat present in the Ars Nova treatise, it was a contemporary—and personal acquaintance—of de Vitry, named Johannes de Muris (Jehan des Mars) who offered the most comprehensive and systematic treatment of the new mensural innovations of the Ars Nova (for a brief explanation of the mensural notation in general, see the article Renaissance music). Many scholars, citing a lack of positive attributory evidence, now consider "Vitry's" treatise to be anonymous, but this does not diminish its importance for the history of rhythmic notation. However, this makes the first definitely identifiable scholar to accept and explain the mensural system to be de Muris, who can be said to have done for it what Garlandia did for the rhythmic modes.

For the duration of the medieval period, most music would be composed primarily in perfect tempus, with special effects created by sections of imperfect tempus; there is a great current controversy among musicologists as to whether such sections were performed with a breve of equal length or whether it changed, and if so, at what proportion. This Ars Nova style remained the primary rhythmical system until the highly syncopated works of the Ars subtilior at the end of the 14th century, characterized by extremes of notational and rhythmic complexity. This sub-genera pushed the rhythmic freedom provided by Ars Nova to its limits, with some compositions having different voices written in different tempus signatures simultaneously. The rhythmic complexity that was realized in this music is comparable to that in the 20th century.

Of equal importance to the overall history of western music theory were the textural changes that came with the advent of polyphony. This practice shaped western music into the harmonically-dominated music that we know today. The first accounts of this textual development were found in two anonymous yet widely-circulated treatises on music, the Musica and the Scolica enchiriadis. These texts are dated to sometime within the last half of the ninth century. The treatises describe a technique that seemed already to be well established in practice. This early polyphony is based on three simple and three compound intervals. The first group comprises fourths, fifths, and octaves; while the second group has octave-plus-fourths, octave-plus-fifths, and double octaves. This new practice is given the name organum by the author of the treatises. Organum can further be classified depending on the time period in which it was written. The early organum as described in the enchiriadis can be termed "strict organum" Strict organum can, in turn, be subdivided into two types: diapente (organum at the interval of a fifth) and diatesseron (organum at the interval of a fourth). However, both of these kinds of strict organum had problems with the musical rules of the time. If either of them paralleled an original chant for too long (depending on the mode) a tritone would result. This problem was somewhat overcome with the use of a second type of organum. This second style of organum was called "free organum". Its distinguishing factor is that the parts did not have to move only in parallel motion, but could also move in oblique, or contrary motion. This made it much easier to avoid the dreaded tritone. The final style of organum that developed was known as "melismatic organum", which was a rather dramatic departure from the rest of the polyphonic music up to this point. This new style was not note against note, but was rather one sustained line accompanied by a florid melismatic line. This final kind of organum was also incorporated by the most famous polyphonic composer of this time—Léonin. He united this style with measured discant passages, which used the rhythmic modes to create the pinnacle of organum composition. This final stage of organum is sometimes referred to as Notre Dame school of polyphony, since that was where Léonin (and his student Pérotin) were stationed. Furthermore, this kind of polyphony influenced all subsequent styles, with the later polyphonic genera of motets starting as a trope of existing Notre Dame organums.

Another important element of Medieval music theory was the unique tonal system by which pitches were arranged and understood. During the Middle Ages, this systematic arrangement of a series of whole steps and half steps, what we now call a scale, was known as a mode. The modal system worked like the scales of today, insomuch that it provided the rules and material for melodic writing. The eight church modes are: Dorian, Hypodorian, Phrygian, Hypophrygian, Lydian, Hypolydian, Mixolydian, and Hypomixolydian. Much of the information concerning these modes, as well as the practical application of them, was codified in the 11th century by the theorist Johannes Afflighemensis. In his work he describes three defining elements to each mode. The finalis, the reciting tone, and the range. The finalis is the tone that serves as the focal point for the mode. It is also almost always used as the final tone (hence the name). The reciting tone (sometimes referred to as the tenor or confinalis) is the tone that serves as the primary focal point in the melody (particularly internally). It is generally also the tone most often repeated in the piece, and finally the range (or ambitus) is the maximum proscribed tones for a given mode. The eight modes can be further divided into four categories based on their final (finalis). Medieval theorists called these pairs maneriae and labeled them according to the Greek ordinal numbers. Those modes that have d, e, f, and g as their final are put into the groups protus, deuterus, tritus, and tetrardus respectively. These can then be divided further based on whether the mode is "authentic" or "plagal." These distinctions deal with the range of the mode in relation to the final. The authentic modes have a range that is about an octave (one tone above or below is allowed) and start on the final, whereas the plagal modes, while still covering about an octave, start a perfect fourth below the authentic. Another interesting aspect of the modal system is the universal allowance for altering B to Bb no matter what the mode. The inclusion of this tone has several uses, but one that seems particularly common is in order to avoid melodic difficulties caused, once again, by the tritone.

These ecclesiastical modes, although they have Greek names, have little relationship to the modes as set out by Greek theorists. Rather, most of the terminology seems to be a misappropriation on the part of the medieval theorists Although the church modes have no relation to the ancient Greek modes, the overabundance of Greek terminology does point to an interesting possible origin in the liturgical melodies of the Byzantine tradition. This system is called oktoechos and is also divided into eight categories, called echoi.

For specific medieval music theorists, see also: Isidore of Seville, Aurelian of Réôme, Odo of Cluny, Guido of Arezzo, Hermannus Contractus, Johannes Cotto (Johannes Afflighemensis), Johannes de Muris, Franco of Cologne, Johannes de Garlandia (Johannes Gallicus), Anonymous IV, Marchetto da Padova (Marchettus of Padua), Jacques of Liège, Johannes de Grocheo, Petrus de Cruce (Pierre de la Croix), and Philippe de Vitry.