Isorhythm

Isorhythm (from the Greek for "the same rhythm") is a musical technique using a repeating rhythmic pattern, called a talea, in at least one voice part throughout a composition. Taleae are typically applied to one or more melodic patterns of pitches or colores, which may be of the same or a different length than the talea.

Isorhythms first appear in French motets of the 13th century such as the Montpellier Codex (Lanford 2011, 9). Although 14th-century theorists used the words talea and color—the latter in a variety of senses related to repetition and embellishment (Sanders and Lindley 2001)—the term "isorhythm" was not coined until 1904 by musicologist Friedrich Ludwig (1872–1930), initially to describe the practice in 13th-century polyphony. Ludwig later extended its use to the 14th century music of Guillaume de Machaut. Subsequently, Heinrich Besseler and other musicologists expanded its scope further as an organizing structural element in 14th and early 15th-century compositions—in particular, motets (Bent 2001; Taruskin 2010, 266). Some of the earliest works organized around isorhythms are early 14th-century motets by various composers in an illuminated manuscript of the Roman de Fauvel. Two of the era's most important composers of isorhythmic motets are Phillipe de Vitry (1291–1361) and Guillaume de Machaut (c. 1300–1377) (Latham 2002). Machaut's Motet No. 2, De souspirant/Tous corps qui de bien amer/Suspiro, is an example of typical 14th-century use of isorhythm (Randel 2003).

Isorhythm is a logical outgrowth of the rhythmic modes that governed most late medieval polyphony. Discarding modal-rhythmic limitations, isorhythm became a significant organizing principle of much of 14th-century French polyphony by extending the talea of an initial section to the entire composition in conjunction with variation of a corresponding color (Editors of the Encyclopædia Britannica 1998). "The playful complexity of ....[taleae] that mixes mensuration and undergoes diminution by half—became a typical, even a defining feature of motets in the 14th century and beyond" (Taruskin 2010, 266).

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