Gregorian chant is the official ecclesiastical music used in the liturgy of the Roman Catholic Church. Written in free-rhythmic form, an even flowing rhythm with no fixed tempo, this chant is sung unaccompanied in solo voice or by several voices in unison. Said lo have been finally arranged by Pope Gregory the Great in the late sixth century, the chant derives its name from him. Consisting of a collection of hundreds of compositions on biblical texts, the use of Gregorian music gradually look the place of the Ambrosian, Gallican, and Mozarabic chants. In the 10th century, Gregorian chant underwent a change when polyphonic compositions, based on the chant, grew in favor. The beginning of the 20th century saw a return to the use of the chant in the Roman church, by demand of Pope Pius X. In 1903, convinced that the Gregorian music was the highest type of sacred musical expression, the Pope issued his
Motu Proprio, a bull ordering a complete restoration of the authentic chant as the official music of the church. The order did not, however, exclude the moderate use of other ecclesiastical music of filling style. A music school, Pius X School of Liturgical Music, was established in New York in 1918 for the purpose of carrying out the Pope's request by a systematic teaching of the chant.
