(cantus), is used for the vocal music of churches.

In church history we meet with divers kinds of chant or song. The first is the Ambrosian, established by St Ambrose. The second, the Gregorian chant, introduced by Pope Gregory the Great, who established schools of chantors, and corrected the church-song. This is still retained in the church under the name of plain song: at first it was called the Roman song. The plain or Gregorian chant, is where the choir and people sing in union, or all together in the same manner.