Rhythmic mode - Definition

In medieval music, the rhythmic modes were patterns of long and short durations imposed on written notes which otherwise appeared to be identical. Since modern notation of duration had not evolved by the early 13th century, composers and singers used instead a method of rhythmic performance based on context; a singer would know which pattern of long and short to apply to a string of notes from the position of those notes within a phrase, and from an introductory notation at the start of the phrase indicating a mode number.

The use of the rhythmic modes is the most characteristic feature of the music of the Notre Dame school, which flourished from the late 12th through early 13th centuries, especially the compositions of Leonin and Pérotin, but they are also predominant in much of the rest of the music of the ars antiqua through about the end of the 13th century. Composition types which were permeated by the modal rhythm include Notre Dame organum (most famously, the organum triplum and organum quadruplum of Pérotin), conductus, and discant clausulae. Later in the century, the motets by Petrus de Cruce and the many anonymous composers, which were descended from discant clausulae, also used modal rhythm, often with much greater complexity than was found earlier in the century: for example each voice sometimes sang in a different mode, as well as a different language.

There were six rhythmic modes, as first explained in the anonymous treatise of about 1240, De mensurabili musica (formerly attributed to Johannes de Garlandia, who is now known to have edited it extensively in the late 13th century). Each mode consisted of a short grouping of long and short note values, corresponding to a metrical foot, as follows:

1. Long-short (trochee)
2. Short-long (iamb)
3. Long-short-short (dactyl)
4. Short-short-long (anapest)
5. Long-long (spondee)
6. Short-short (pyrrhus)

Modern transcriptions of the six modes usually are as follows:

1. Quarter, eighth (generally barred, therefore, in 3/8)
2. Eighth, quarter (barred in 3/8)
3. Dotted quarter, eighth, quarter (barred in 6/8)
4. Eighth, quarter, dotted quarter (barred in 6/8)
5. Dotted quarters (barred in either 3/8 or 6/8)
6. Eighths (barred in 3/8 or 6/8)

An individual occurrence of any one of these patterns is known as an ordo.

After recognizing which of the six modes applied to a passage of neumes, a singer would generally continue on in that same mode until the end of a phrase, or a cadence.

Other writers who covered the topic of rhythmic modes include Anonymous IV, who is the principal source on the music of Leonin and Pérotin, and Franco of Cologne, who recognized the limitations of the system and was the first to propose a notational method whereby the duration of any note would be signified by its shape.

References and further reading

• Articles "Rhythmic mode", "Johannes de Garlandia," "Franco of Cologne," in The New Grove Dictionary of Music and Musicians, ed. Stanley Sadie. 20 vol. London, Macmillan Publishers Ltd., 1980. ISBN 1561591742
• The New Harvard Dictionary of Music, ed. Don Randel. Cambridge, Massachusetts, Harvard University Press, 1986. ISBN 0674615255
• Richard H. Hoppin, Medieval Music. New York, W.W. Norton & Co., 1978. ISBN 0393090906