Jan Hajic jr., Vojtech Lanz, Gustavo Ballen

Gregorian chant was a central musical tradition in Medieval Latin Europe and one of the expressions of its cultural unity: any Latin Christian liturgy, such as the weekly Sunday mass, would have involved Gregorian
chant as a major part of the prescribed ritual. The Gregorian legend of chant melodies’ divine origin required the practitioners to conserve them, to the extent that this requirement motivated the development of exact pitch notation. Nevertheless, surviving written sources document a considerable melodic diversity. Some systematic patterns within this melodic diversity have previously been observed in chant scholarship, especially during efforts to build a critical edition reconstructing the earliest possible forms of chant melodies with philological approaches. Taking an evolutionary perspective, we notice analogies between biological evolution and processes of chant transmission, which lead us to suggest recovering these “melodic dialects” using phylogenetic methods instead. In this paper, we show that phylogenetic models recover historically plausible patterns of chant melody evolution. We observe that some, but not all, institutional networks play a more important role than geographic proximity. Phylogeny is shown to be a viable class of methods for studying chant melody, and we discuss next
steps for a more comprehensive evolutionary approach to chant.