| May 17, 2012

The words “hemiola” and “sesquialtera” both signify the ratio 3:2, and in music were first used to describe relations of pitch. Dividing the string of a monochord in this ratio produces the interval of a perfect fifth. Beginning in the 15th century, both words came to be used also to describe rhythmic relationships, specifically the substitution usually through the use of coloration of three imperfect notes for two perfect ones in tempus perfectum or in prolatio maior.[4]

via Hemiola – Wikipedia, the free encyclopedia.