(cantus, a song), the word employed in the early Church to designate the vocal music of the congregation. The term was applied, later, to special tunes adapted to prose; e.g. the Ambrosian, established by St. Ambrose, and the Gregorian, introduced by Pope Gregory the Great, who established schools of chanters, and corrected the Church music. This, at first, was called the Roman song; afterwards the plain song, as the choir and people sing in unison. In modern liturgical worship, the word designates the musical performance of all those parts of a prose liturgy which are permitted to be sung or recited in a musical tone. In a wider sense, it is used to denote those forms of sacred music in which prose (e.g. passages of Scripture) is sung in simple harmonies. SEE MUSIC.