St. Gregory was born in Rome circa 540 A.D. and reluctantly became Pope in 590, when he would have preferred to remain a monk. There is little concrete evidence to support his being the composer of the Catholic Antiphonary, but it is certainly agreed among scholars that Gregory was the first to compile and order the pre-existing singular chants into a coherent whole.
Gregorian chant has been used around the world in the Roman Catholic liturgy for over a thousand years. It is most closely associated with the Benedictine order of monks, who would use Gregorian chants daily in services and in prayer. The Gregorian tradition superseded the Ambrosian, Gallican, and Mozarabic chants between the eighth and 11th centuries, except in Milan, where the Ambrosian chants are used to this day. The chants formed part of the day to day worship; the choir, clergy and congregation would sing prayers instead of saying them.
In modern Catholicism, as of 2010, the chants are used less frequently in worship. Often the choir will sing certain parts of the service -- an introit, key prayers and the text of the mass -- but rarely does the congregation join in. The chants offer some change of pace to the worship instead of forming the key liturgical substance.
Gregorian chant is also used as concert repertoire with groups such as The Canterbury Gregorian Music Society and The Schola Gregoriana of Cambridge specializing in authentic interpretations.
Gregorian chant, like other types of plainchant, is notated on a four line stave. A clef is placed at the beginning of each system, on the line that corresponds to "do," the first note of the Ionian mode (the modern major scale). This defines the tonality of the chant. Rhythm is denoted by a range of different "neumes" which all look different and refer to different lengths or progressions of notes. However, Gregorian chant has no true meter.
Gregorian chant melodies have had a wide influence on classical music. The 19th and 20th century French composers such as Debussy, Durufle and Poulenc often used extracts of Gregorian chant in their pieces, as did Edward Bairstow in his well known anthem "Blessed City, Heavenly Salem."