Sancti Dei Omnes - commemoration of All Saints in the Little Office of the Blessed Virgin Mary

https://gregobase.selapa.net/chant.php?id=14253

This is a bit that was removed in the 1962 revisions. It's a remnant of the lesser known of the three little Offices from medieval times: Office of All Saints, Office of the Dead and Office of Our Lady. Because praying the Divine Office plus all the Little Offices was prohibitive, some opted for just the Office of the Dead and others favoured Our Lady plus a commemoration of All Saints.

https://www.buymeacoffee.com/veronicab