This is Jenny O’Brien’s setting of the Reproaches.
She has two sections of chant for cantors and two refrains for the assembly.
I’ve done a backing with guessed chords for the first refrain.
My people, what have I done to you?
Or how have I grieved you? Answer me!
Then there are three verses for a cantor followed by a Greek refrain.
This is even more approximate.
Hagios o Theos, Hagios Ischyros, Hagios Athananatos, eleison himas.
There are then five more verses for the cantors.
You then finish with the original refrain. It looks epic but I can’t find anything on the net to show off the whole piece.