The playful complexity of this tenor—an arbitrary (that is, “rational”) talea that mixes mensurations and undergoes diminution by half—became a typical, even a defining feature of motets in the fourteenth century and beyond. Modern scholars use the term isorhythm (“same-rhythm”) to denote the use of recurrent patterns or taleae, often quite long and cunningly constructed, that do not rely on traditional modal ordines. Motets that employ such recurrent patterns—often, as here, varied schematically on successive colores, or even within a color—are called isorhythmic motets. Despite the Greek derivation of the term, it is a modern coinage and a German one, first used by the great medievalist Friedrich Ludwig in 1904 in a pioneering study of the motets in the Montpellier Codex.
The first piece to which the term was applied, as it happens, was On a parole/A Paris/Frese nouvele, familiar to us from the previous chapter (Fig. 7-9/Ex. 7-9). Yet according to current standard usage, that motet is not isorhythmic; the motetus, which Ludwig mainly had in mind, moves in phrases that are rhythmically similar but not identical, and in the tenor the color and the talea are coextensive, amounting to a simple melodic repetition. As currently used, the term isorhythm implies literal rhythmic repetition that, while often coordinated with melodic repetition (chiefly in tenors), is nevertheless independently organized.
A true isorhythmic tenor, like the one in Ex. 8-3, is built on two periodic cycles, the one governing pitch, the other duration. And this implies the separate, hence abstract, conception of melodic and rhythmic successions. The passages of tenor-coloration in this motet by Vitry are accompanied, as we have seen, by rhythmic recurrences in the upper parts as well, so that this particular isorhythmic motet has patches of “pan-isorhythm,” in which all the voices are bound periodically (which of course means predictably) into recurrent patterns to which the ear cannot help looking forward.
Thus isorhythm and its attendant effects have at once an embellishing and a symbolic purpose. They enhance surface attractiveness, particularly when smaller note-values and hockets are called into play. At the same time the periodicities thus set in motion reflect the periodicities of nature (celestial orbits, tides, seasons), giving the senses—and, through the senses, the mind—an intimation of the ineffable musica mundana. The coordination of surface and deeper structure that this motet so well exemplifies, and their conjoint appeal to sense and reason, may all be subsumed under the heading of rhetoric—the art of (musical) persuasion. That was the all-encompassing aim to which every detail of the ceremonious late-medieval motet was geared, whether at the level of grandiose architecture or that of seductive detail. That rhetoric found its most eloquent expression in motets of doctrinal, civic, or political cast.
- Citation (MLA):
- Richard Taruskin. "Chapter 8 Business Math, Politics, and Paradise: The Ars Nova." The Oxford History of Western Music. Oxford University Press. New York, USA. n.d. Web. 1 Jul. 2016. <http://www.oxfordwesternmusic.com/view/Volume1/actrade-9780195384819-div1-008009.xml>.
- Citation (APA):
- Taruskin, R. (n.d.). Chapter 8 Business Math, Politics, and Paradise: The Ars Nova. In Oxford University Press, Music from the Earliest Notations to the Sixteenth Century. New York, USA. Retrieved 1 Jul. 2016, from http://www.oxfordwesternmusic.com/view/Volume1/actrade-9780195384819-div1-008009.xml
- Citation (Chicago):
- Richard Taruskin. "Chapter 8 Business Math, Politics, and Paradise: The Ars Nova." In Music from the Earliest Notations to the Sixteenth Century, Oxford University Press. (New York, USA, n.d.). Retrieved 1 Jul. 2016, from http://www.oxfordwesternmusic.com/view/Volume1/actrade-9780195384819-div1-008009.xml