Rhythmic Modes
A 13th-century system of rhythm, characterized by the consistent repetition
of certain simple rhythmic patterns in ternary meter. Usually six
modes are distinguished, as shown below. In musical compositions,
the patterns were reiterated a number of times, depending on the length
of the phrase or, in medieval terminology, on the "ordo." The "ordo"
indicated the number of times a pattern was repeated without interruption.
The modes are the rhythmic basis of the organa,
clausulae,
and motets of the 13th century.
Usually the first, second, and sixth modes occur in the upper parts, and
the third and fifth in the lower. The fourth was rarely used. In
practice, certain modifications of the normal patterns were admitted, such
as occasional omission of a weak beat or breaking up of one note into two
or three.
