A Dictionary of Music and Musicians/Sesqui
SESQUI. A Latin word, signifying, literally, the whole plus its half.
In musical terminology, the prefix Sesqui is used, in combination with certain numeral-adjectives, to express the Proportion, either of Harmonic Intervals or of rhythmic combinations. [See Proportion.] Thus, Sesquialtera expresses the Proportion of two to three, and therefore represents the Perfect Fifth, which is produced by sounding two-thirds of a given string. Sesquitertia, expressing the Proportion of three to four, represents the Perfect Fourth, sounded by three-fourths of the string. Sesquiquarta, or four-fifths, represents the Major Third. Sesquiquinta represents the Minor Third, given by five-sixths of the resonant string. Sesquisexta, six-sevenths, and Sesquiseptima, seven-eighths, correspond with no Intervals in the accepted Canon of the Scale: but, Sesquioctava, or eight-ninths, represents the peculiar form of the Major Second known to Theorists as the Greater Tone; and Sesquinona, nine-tenths, gives the Lesser Tone an Interval, which, though conventionally called a Major Second, and treated, in practice, as identical with that just described, is less, by one Comma, than the Tone represented by Sesquioctava.[1]
In rhythmic combinations, Sesquialtera is used as the general symbol of Triple Time. The term Sesquialtera is also applied to passages of three notes sung against two; Sesquitertia, to three notes sung against four; and Sesquiquarta, to four notes sung, or played, against five. [See Hemiolia.]- ↑ The Greater and Lesser Tones are, by some theorists, called the Acute and the Grave Major Second.