The Kyrie ("Lord have mercy"), which follows the Introit of the Mass, is a rare survival of the Greek rite in the Latin liturgy. Originally a litany, calling for additional words, in its simplest form it was repeated three times in the Mass. In later musical settings of the Mass, the simplicity of the text allowed more complex treatment. This CD features ten different versions, including two by J.S. Bach, and other liturgical works.