A Dictionary of Music and Musicians/Hemiola
HEMIOLIA (Gr. Ἡμιόλιος; Lat. Sesquialtera; Ital. Emiolia; Fr. Hemiole). Literally, the whole and a half; technically, the proportion of two to three. In this latter sense the word is used, in the musical terminology of the Middle Ages, to denote the Perfect Fifth, the sound of which is produced on the monochord by two-thirds of the open string. The term is also applied by writers of the 16th century to certain rhythmical proportions, corresponding to the triplets of modern music. Thus, three minims, sung against two, are called Hemiolia major; three crotchets (semiminime) against two, Hemiolia minor. Italian writers of later date call 3-4 time Emiolia maggiore, and 3-8 Emiolia minore.
[ W. S. R. ]