domesticus
Lupus non curat numerum ovium
A very useful article in Dumbarton Oaks Papers 56 (2002) by ROSEMARY DUBOWCHIK under the title, Singing with the Angels: Foundation Documents as Evidence for Musical Life in Monasteries of the Byzantine Empire. She uses monastic foundation documents to demonstrate the significant role of church music for the life inside monasteriew between 8th c. and 1448. It's here