The extant fourteenth-century contrapunctus manuals are concerned almost exclusively with counterpoint in two parts, but one treatise, “Quicumque voluerit duos contrapuncti,” sheds light on three-voice composition and lays the groundwork for a refined classification of sonority types in Guillaume de Machaut's nineteen three-voice motets. Building initially upon Sarah Fuller's work, the proposed schema introduces a more nuanced approach to categorizing the intervallic content of consonant and dissonant sonorities. Moreover, by calling attention to the outer voices of certain sonority types, the classification highlights salient structural and aural differences. A systematic study of sonority usage in Machaut's motets also reveals his preference for particular combinations of intervals over others.
An examination of passages from several motets illustrates the classification's potential. A discussion of Motet 7's opening describes the relationship between the underlying contrapunctus and various sonority types, consonant and dissonant, and advances a broader definition for the directed progression. An anomalous progression in Motet 18 suggests that the careful study of sonority may contribute to our current understanding of motet chronology. An analysis of several passages from Motet 4 illustrates how the proposed nomenclature may offer a more nuanced understanding of musical syntax, particularly at phrase endings.