clausula

An interpolation in regular rhythm into 12th- and 13th-century organum, without words, but either sung to the syllable of the text immediately preceding it or played by instruments or both together. The lowest (tenor) part, which in the main portions of the music is in very long notes, here moves at a quicker speed, the notes being arranged in a rhythmical pattern. Numerous clausulae were also designed apparently as independent pieces. In later usage the term meant ‘cadential formula’.