The interpretation of chromatic content in fourteenth-century music has been widely debated. While most studies have focused on contrapuntal necessity, this study advocates an approach that begins from the perspective of melody. Using the ballades, virelais and rondeaux of Guillaume de Machaut as a central repertory, it proposes that not only are chromatic inflections in Machaut's monophonic songs derived melodically, but that many chromatic inflections in Machaut's polyphonic songs also arise from melodic rather than contrapuntal requirements. Because of their implied semitone motion – arguably crucial to tonal organization – they can have an impact on the definition of tonal structure by privileging the individual pitches they decorate, particularly but not exclusively in cadential melodic formulas or progressions.