The Improperia are a series of antiphons and responses, expressing the remonstrance of Jesus Christ with his people. Also known as the Reproaches, they are sung In the Catholic liturgy as part of the observance of the Passion, usually on the afternoon of Good Friday. In the Byzantine Rite, they are found in various hymns of Good Friday and Holy Saturday. The Improperia appear in the Pontificale of Prudentius (846–61) and gradually came into use throughout Europe in the eleventh and twelfth centuries, finally being incorporated into the Roman Ordo in the fourteenth century. Roman Rite In their present form in the Roman Rite, the Improperia are a series of three couplets, sung antiphonally by cantors and followed by alternate Greek and Latin responses from the two halves of the choir; and nine other lines sung by the cantors, with the full choir responding after each with the refrain "Popule meus, quid feci tibi? ..." Besides the Kyrie, this is the only usage of the Greek language in the Roman Rite. Thus the Improperia begin with this couplet that includes parts of the Trisagion: Cantor 1: Popule meus, quid feci tibi? Aut in quo contristavi te? Responde mihi. Cantor 2: Quia eduxi te de terra Ægypti: parasti Crucem Salvatori tuo. Choir A: Hagios o Theos. Choir B: Sanctus Deus. Choir A: Hagios Ischyros. Choir B: Sanctus Fortis. Choir A: Hagios Athanatos, eleison hemas. Choir B: Sanctus Immortalis, miserere nobis. My people, what have I done to you? How have I offended you? Answer me! I led you out of Egypt, from slavery to freedom, but you led your Saviour to the cross. Holy is God! Holy is God! Holy and strong! Holy and strong! Holy immortal One, have mercy on us. Holy immortal One, have mercy on us. The second couplet is sung antiphonally by two cantors of the second choir, and the third couplet by two cantors of the first choir; after each the two choirs respond as above. The nine following reproaches are sung alternately by the cantors of each choir, beginning with the second, with the full choir responding after each reproach with the line, "Popule meus ...": Cantors 3 & 4: Ego propter te flagellavi Ægyptum cum primogenitis suis: et tu me flagellatum tradidisti. Choirs A & B: Popule meus, quid feci tibi? Aut in quo contristavi te? Responde mihi. Cantors 1 & 2: Ego eduxi