- Dolores Pesce
A term first used by Guido for the relationship between certain tones in the medieval gamut, specifically between a modal final and a tone a fifth above or a fourth below (sometimes referred to as the affinalis); specifically, each pair of tones, such as d and a, share a particular pattern of surrounding tones and semitones within the six-note diatonic segments c–a and g–e′. This concept was recognized earlier, though not as systematically, by Hucbald and the authors of Musica enchiriadis and Scolica enchiriadis (who used the term socialitas) and by the anonymous author of the Dialogus de musica (who used similitudo). By recognizing this feature of their gamut, theorists were able to reconcile an inherited chant repertory with the eight-mode system. Specifically, it allowed them to preserve chants with aberrant tones by notating them at the position of the affinalis, where the same tone–semitone arrangement prevails; for example, a first-mode chant with a B♭ (theoretically non-existent) could be notated at the ...