Liturgical music of the Roman Catholic church consisting of unaccompanied melody sung in unison to Latin words. It is named for Pope Gregory I, who may have contributed to its collection and codification and who was traditionally represented as having received all the melodies directly from the Holy Spirit. Of the five bodies of medieval Latin liturgical music, it is the dominant repertoire, and the name is often used broadly to include them all. Gregorian chant apparently derived principally from Jewish cantillation, with other elements entering from the Eastern Church (seeByzantine chant) and elsewhere. Chant has traditionally been performed at the mass and the canonical hours (the eight prayer services traditionally held daily in monasteries). Its texts come primarily from the biblical psalms, metrical hymns, and texts specific to the mass and the hours. The melodies are classified as belonging to one or another of the eight church modes. Chant rhythm is not strictly metrical, and its notation does not indicate rhythm. Since the Second Vatican Council, the performance of chant has diminished greatly. See alsocantus firmus.