Improperia

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.

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? . . . ." Thus the Improperia begin with this couplet that includes parts of the Trisagion:

Cantor 1: Popule meus, quid feci tibi? Aut in quo constristavi 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 hymas.
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.

...
Wikipedia