According to medieval sources, Birgitta’s confessor and collaborator magister Petrus Olavi of Skänninge († 1378) is pointed out as the originator of the sisters’ Divine Office Cantus sororum. Petrus’ authorship has been debated and contested but also accepted by scholars to various degrees. That he did not compose the complete corpus as we know it today is clear, but to what extent he is responsible for texts and musical compositions is difficult to establish, in particular in a world where borrowings and adaptations were the norm and copyright not a problem. Another problem lies in that we not have one single source with musical notation earlier than ca 1450, meaning about 70 years after magister Petrus’ death. In fact nothing is known about what the liturgy and music looked like at the official opening of Vadstena abbey in 1384. 

This paper aims at looking at the origin of Cantus sororum where instead the presumed collective efforts in Rome and Vadstena during the first decades of the abbey’s existence are considered. Questions the paper seeks to address are: What other people and groups could have been involved in the creation of Cantus sororum? What is the content in the earliest notated sources? When became Cantus sororum a fixed repertoire, ready for dissemination to other Birgittine abbeys?  Why are there no earlier sources than from about 70 years after the foundation of the order? How and by whom did the dissemination of the repertoire take place?