Kyrie eleison

The Kyrie eleison is an ancient phrase that has been used in the Christan faith since the 4th century. Its origins can be traced back to the early Christian Church in the eastern Mediterranean, where Greek was a common language. The phrase became a universal expression of faith and repentance as Christianity spread throughout the Roman Empire. 

The acclamation Kyrie eleison (Lord have mercy!) antedates Christian worship and is the one part of western liturgy that remained in Greek throughout the Middle Ages. It was used in various forms of pagan worship including the imperial cult in which the emperor was called Kyrios (lord). Since Christians early on adopted the title lord to call on Jesus of Nazareth whom they believed to be God's annoined (that is to say Christ or Messiah), the acclamation kyrie eleison was quickly incorporated into Christian worship. The fourth- century nun Egeria reported in her Travels (25: 5) that worshippers employed the acclamation during the lamp lighting ceremony of vespers in Jerusalem. Christians principally employed the acclamation as a popular response in litanies. A deacon or other liturgical leader would intone a short supplication, and the assembly would respond kyrie eleison. In Rome, litanies with kyrie eleison were sung after antiphonal psalms at the end of long processions on important holidays to the stational churches. The incorporation of the kyrie into the opening rites of the Mass appears to be in imitation of these large-scale processions. The solemn entrance into the Mass became a short version of the stational processions, one psalm (the introit) followed by a litany with the response kyrie eleison. By the sixth century, Pope Gregory the Great tells us that the litanic form was dropped on weekdays and only the three-fold or nine-fold singing of kyrie eleison was left. Gregory also mentioned the custom of alternating the kyrie eleison with a new acclamation Christe eleison.

Like the Gloria in excelsis the Kyrie eleison was sung to hundreds of different melodies across Europe. The first sources with notation contain both melodies that have only the acclamations Kyrie eleison and Christe eleison as well as melodies that contain both Latin verses and the Greek acclamations.