Isorhythm

Isorhythm (iso or same) consists of an order of durations or rhythms, talea ("cutting", plural taleae), which is repeated within a tenor melody whose pitch content or series, color (repetition), varied in the number of members from the talea. The term was coined in 1904 by Friedrich Ludwig to describe this practice in 14th and 15th century polyphonic motets but is also used in motets of the middle ages, the music of India, and by modern composers such as Alban Berg, Olivier Messiaen, and John Cage. It may be used in all voices or only a few voices. In motets, it began in the tenor voice but was then extended to higher ones.

Friedrich Ludwig applied it again in 1910, still for the 13th century, to successive phrases of equal length but not necessarily the same rhythm, a phenomenon whose 14th-century use Besseler called 'isoperiodic' (the German noun is Isoperiodik), meaning that 'the upper voices only follow the plan of the lower voices in a general way or have merely a few bars rhythmically identical in each Tenor period'. Isoperiodicy, unlike isorhythm, cannot survive diminution of the overall lenth of a phrase. Sanders developed the idea of modular numbers to represent the periodic construction of motet upper voices bounded by rests (Grove 6; 1973), sometimes non-coincident, or offset (Isorhythm. Bent, Margaret. Grove, 2nd ed. vol. 12 page 621).

The earliest Italian uses of rhythmic repetition are not in motets but in madrigals: Landini's Si dolce non sono and Lorenzo da Firenze's Povero zappator, in which short units are immediately followed by their own diminutions and the resulting larger patterns are repeated. Only after 1400 did isorhythm enter the Italian tradition of ceremonial and occasional motets (Bent, 1992; Allsen, 1992, chap. 3). In each half of Ciconia's motet Petrum Marcello the tenor follows the undiminished form immediately with its diminution, while in two other motets Ciconia makes the second half an undiminished rhythmic replication, in all voices, of the first (Isorhythm. Bent, Margaret. Grove, 2nd ed. vol. 12 page 621).

Ars nova composer Philippe de Vitry has been credited with the invention of the technique, but it "was neither an invention of Philippe de Vitry nor his exclusive property in the early fourteenth century." The isorhythmic construction was often varied through the use of strict or free rhythmic diminuation in the repetition of the color. (Hoppin 1978, p.363)

The talea was often a rhythmic mode. The color of isorhythm may be compared with the tone row of the twelve-tone technique's fixed order of pitches and varied durations. The modern musical innovation of integral serialism in the classes of Olivier Messiaen sprang from a study of the 12 tone compositions of Anton Webern and the isothythmic organization within motets of Guillaume de Machaut.

Coloration also refers to otherwise perfect notes colored red or with an open notehead to indicate the loss of 1/3 their duration, making them imperfect.

Source

*Hoppin, Richard H. (1978). Medieval Music. New York: W.W. Norton & Co. ISBN 0393090906.

External links

*Here Of A Sunday Morning WBAI 99.5 FM: Isorhythm
*Isorhythm and Hocket in Guillaume de Machaut's Hoquetus David By Mark A. Zobel, Paper Presented at the University of Colorado Doctoral Research Seminar on Black-Note Mensural Notation, Boulder, Colo., April 1999
*London Sinfonietta's Isorhythm composition game