Gioseffo Zarlino (March 22, 1517 - February 14, 1590), was an Italian music theorist and composer. While he studied with Adrian Willaert and composed a number of masses, motets and madrigals, his principle claim to fame is as a music theorist. He advocated division of the octave into twelve parts, and while Pietro Aaron may have been the first theorist to describe a version of meantone, Zarlino seems to have been the first to do so with exactitude, describing 2/7-comma meantone in his Le istitutioni harmoniche in 1558. In his Dimonstrationi harmoniche of 1571, he revised the numbering of modes to emphasize C and the Ionian mode, thereby drawing closer to the harmonic and melodic system basing itself on tonality and the major and minor scales. His most notable student was the music theorist Vincenzio Galilei, the father of Galileo Galilei.
