Little is known of Manuel Chrysaphes' life, except that he was a highly influential composer and musician in the final days of the Byzantine Empire. He survived the Ottoman conquest of the Empire and may have moved to Greece. Much of his liturgical music has survived, as well as a treatise on chant.
His work, including the haunting Ο Θεός ήλθοσαν έθνη (commonly called the "Lament for the Fall of Constantinople"), commonly features an ison, which functions basically as a drone, but does move around and create different harmonies.
ἐγὼ σήμερον γεγέννηκά σε
("Today I Have Begotten Thee")
Ο Θεός ήλθοσαν έθνη
("Lord, Foreign Nations Have Entered Thy Temple")