In the mid-fourteenth century the Black Death inflicted one of the most devastating losses of life in human history. This was met by exercises of collective piety such as the singing of psalms and the celebration of special votive masses, which encouraged social cohesion in the face of the tragedy. This article presents results from an analysis of fifty-seven manuscripts containing copies of the monophonic ‘Recordare domine’ Mass, reportedly created at the behest of Clement VI at Avignon during his Black Death-spanning pontificate. Of these, seven manuscripts contain fully notated renditions of each of the chants for the Mass Propers, enabling us to decouple questions concerning the organisation and transmission of the melodies from those of the texts set to them. When the different versions of the Mass are compared, two major findings emerge. First, differential patterns of consistency within the texts and melodies suggest that the texts of the ‘Recordare domine’ Mass may have circulated separately from the melodies set to them, with the choice of music left to the discretion of the local performing clergy. Second, the patterns of variation between different versions of the Proper texts and melodies allow us to see how a variety of composition strategies (including mnemonic processes) were used to create new music for the mass. The ‘Recordare domine’ Mass thus sheds light not only on the performance of organised sacred music at a pivotal point in European history, but also more generally on the processes of chant composition as a tool for use in response to social stress.