Attached is Markos Vasileiou's transcription of Manuel Chrysaphes' lament, Ο Θεός ήλθοσαν έθνη, as published in the liner notes of Manolis Chatzegiakoumes' Symmeikta #6 (already uploaded somewhere previously on the Greek site of Ps.). For this recording / publication, see:
The original can be found written in Chrysphes' hand in MS Iviron 1120 (copied in 1458), on fols. 451r-452r, preceded by the phrase: "Another. Composed after the Fall of C/ple by Manuel Chrysaphes the lampadarios."
The text (from some old notes, forgive any inaccuracies):
Here is the translation of the Prologue, written by Mitri's son, Fou'ad (the publisher of the "Spiritual Psalter", vol. 3): O God, the nations have invaded your inheritance
Manuel Chrysaphes, the composer of this marvellous historical piece, which has been discovered at the beginning of the first world war, did not find more eloquent words than those of Psalm 78 in order to mourn in it the church of Aghia Sophia after it had been turned into a mosque. My father transposed it freely into arabic and he used to perform it during the festal Liturgies instead of the Koinonikon.