During the Renaissance period, it was very common for composers to write Mass settings that used popular songs as melodic sources; the cactus firmus would be the popular melody, and a whole large-scale choral composition would elaborate upon it. For this Mass, the Franco-Flemish composer Jean Richafort used the melody of a song called “Dictes moy toutes voz pensées” (archaic French for “tell me all your thoughts”) to create a lush and somber masterpiece of religious music, sung beautifully here by the Tallis Scholars.