This Christmas Office Hymn from the 6th century is set to a hymn by Monteverdi in his Selva Morale e Spirituale in 1640-1. Monteverdi, who had lived and worked in Venice for thirty years by that point could be said to have curated his achievements there in this bumper volume featuring all kinds of his music.

He said that this particular music could be used for any hymn in this metre and the words of another hymn; ‘Deus tuorum militum’ are underlaid in the Selva Morale collection.

There are three vocal lines and originally the accompaniment would have been on violins although in Carols for Choirs, bk 3, from which I took this hymn gives piano or organ as the accompaniment.
This hymn would have been used for First Vespers during Christmas.