Prokeimenon

In the liturgical practice of the Orthodox Church and the Byzantine Rite, a prokeimenon (GreekΠροκείμενον, plural prokeimena; sometimes prokimenon/prokimena; lit. 'that which precedes') is a psalm or canticle refrain sung responsorially at certain specified points of the Divine Liturgy or the Divine Office, usually to introduce a scripture reading. It corresponds to the Gradual of the Roman Mass.