The use of contrafact as a compositional tool was a common practice in the Middle Ages, and contrafact chants comprise an essential part of the repertoire of late medieval liturgical chant. To date, however, the definitions and descriptions of this technique do not take sufficient account of established compositional practice in its entirety, as developed by composers in the late Middle Ages. This project therefore aims to conduct the first systematic examination into the creation and dissemination of late liturgical contrafacts in the late Middle Ages, with the aim of showing the compositional methods used and defining the approaches taken by different composers.