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Project 9 Examples Research, Part 2: Descant, Post-Guidonian Organum, and the Rise of Modal Rhythm

Continuing on from the last post, in the post-Guidonian period, starting around the second half of the 11th century, organum began changing.

Beginning with Ad organum faciendum, we see that organum at the fifth and organum at the fourth were no longer distinguished. Instead, the treatise offers one organum in which fourths and fifths are intermixed. Position of the vox organalis was now above and not below the vox principalis, and the voice-crossing appears more often, unlike the earlier, Guidonian practice when it could only appear if the principal voice goes below the lower pitch limit – what was called organum suspendum. In terms of the melodic shape, not only were parallel and oblique motions combined, without the drones for the latter, but we also see contrary motion being introduced. Because of this mixture of melodic movements, this type of organum may be termed free organum.

While the appearance of the oblique organum was justified by the avoidance of tritones which could occur in the parallel motion of the fourths, the principle behind free organum doesn’t involve the symphoniae (term for consonants, see the previous post). Instead, it is guided by the Guidonian doctrine called affinitas vocum. (Fig. 1)


Fig. 1. The illustration of Guido’s affinitas vocum

It shows that the seven pitches available at the time were not completely independent, but relate to each other in four final patterns – modi vocum. For example, A and D have a tone below and a tone, semitone and two tones above. Similarly, B and E have to two tones below and a semitone and two tones above. It is interesting that the affinities exist only between pitches that are a fourth or a fifth apart. And so, in organum, the vox organalis became a response in which any pitch possesses affinity with the given cantus pitch. Here are two videos of the free organum:

Gradually, towards the 12th century, the new principle of contrary movement began taking more significance. John Cotton, for example emphasized this type of motion and writes: “whenever original melody rises, the organal part should descent and vice-versa.” The resulting form is called the contrary organum.

Mid-12th century was the beginning of the period known as Ars Antiqua, which brought about a new type called melismatic organum, emerging at the abbeys of Santiago de Composetalla in Spain and Saint-Martial of Limoges in France. In melismatic organum, a single note of the principal voice was held against a decorative group of notes of the organal part, with the length of this group varying from a few notes to lengthier melismas. As such, the principal voice became a succession of held, sustained tones of the plainchant, which was named later, in the 13th century, tenor.

What is interesting is that vox organalis, what was originally only an added voice, now became the essential feature of the style, while vox principalis, once the principal part, seems now to only support the organal voice. Another interesting thing is that the new style of melismatic organum retained the name old organum, while the older tradition of note-against-note organum now received the newer term discant as its name.

Unlike the melismatic notes of the organum, in discant, the organal, or now called the discant voice rather, still depended on the movement of the tenor, so that intervals between voices had to remain being strictly controlled. Compared to the older theory though, the use of the fourth receded gradually, being replaced by the third and the sixth. At first, the two intervals are observed to be used only when they moved directly towards the symphonias, known now as the perfect consonance. With the gradual acceptance of the thirds and sixths into the category of consonances, although as imperfect ones, we see more and more of their free usage without this rule, while the dissonances came to be allowed as passing tones and appoggiaturas, as described by Johannes de Garlandia c. 1250.

Of course, it took a while for these new principles of consonance and dissonance to become fixed, and the same is true for the form, which in the later St. Martial manuscripts developed into cases of transitional organum, where we find a mixture of discant and the melismatic organum sections within the same composition. Beside these changes, there was also a continual shift in notation, which generally accompanied the history of organum/discant, and at this moment of history, the note length is developing into a more and more important component of the rhythm.

The point of maturity was reached in Notre Dame in the 13th century, when organum became a sophisticated musical form. The organum duplum developed under Leoninus, who made Magnus Liber Organi. The plainchant of organum duplum was restricted to solo sections of Graduals, Alleluias, responsories and the Benedicamus Domino. Unlike the St. Martial examples, in the Notre Dame school, the notes in discant, also called clausulae, were rhythmicized, based on precise triple meter patterns of six rhythmic modes from the classical metrics of poetry. Hence, Leoninus provided the first notation for the rhythmic notation and introduced the first step towards the standardization of relative amount of movement when various voices were sound. On the other hand, the melismatic organum remained in the old, free melodic flow of neumes.

The organum composition could include both of these sections. Benedicamus Domino illustrates this very well. Usually, where the chant is syllabic – Benedicamus, this allows for the tenor to be held, resulting in the melismatic organum. Contrary to this, where the chant is melismatic – Domino, this allows for the tenor and the upper voice, with the new name duplum, to move at the same rate, making the discant. There was also a third style, a brief copula, which connected the tenor of the unmeasured melismatic organum and the patterned rhythmic modes of discant in the upper voice, being a type of bridge between the two. Melismatic organum, discant and copula can also be understood not only as sections, but the musical textures which can be found in the polyphonic compositions of the time.

While Leoninus was named the greatest composer of the melismatic organum, Perotinus, his pupil, was called the greatest composer of discant. He composed longer discant clausulae and copula passages, and added the third voice – organum triplum, and there are even three of his examples of four voices – organum quadruplum. More significantly, with Perotinus, the non-modal sustained-note style of the melismatic organum started to be repressed from the polyphonic development.

With the rise of the modal rhythm, discant not only gained a hold and modified all musical forms of the period, but also created new forms such as conductus, independent of plainchant, and motellus, which arose by adding a new text to clausula in the upper parts, leading into the important future genre – motet. Discant became the focal point of the fore-coming, Ars Nova composers, bringing the new possibilities such as further rhythmic divisions and techniques like hocket, imitation, and voice-exchange. In this period, discant was designated as contrapunctus in the early treatises of the Vitry school and of Johannes de Muris. With this, it received the general meaning of the combination of sounds, and the rules of consonance and dissonance in discant soon became the rules from part-writing in counterpoint. However, after the 15th century, contrapunctus took dominance as the term for polyphony.

In England though, the term differed a bit from the Continent. More about that, as well as the later connotations of the term discant/descant, read my next post.

List of illustrations:
Figure 1. The illustration of Guido’s affinitas vocum


Johannes (de Garlandia) (1978) Concerning Measured Music (De Mensurabili Musica). Colorado Springs: Colorado College Music Press

Reimer, Erich (1972) Johannes de Garlandia, De mensurabili musica: Quellenuntersuchungen und Edition, Part 1. Stuttgart: Steiner

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