Europeans began writing down music in the ninth century as an aspect of thepowerful orientation toward scriptuality that characterized the Carolingianculture. Whether as a matter of chance coincidence or not (I think not),medieval writing about music began, as far as we know, inthe same century and under the same cultural and political circumstances. Toget a sense of what the musically curious and informed thought should andcould be described and explained, we can consult the oldestcomprehensive—and most widely transmitted—didactic manualabout music that has come down to us from the Middle Ages, theMusica enchiriadis (“Handbook of Music”),written about 900 C.E. by an anonymous author.

For a hint of what the author might have meant by “qualities,”in reference to music we can read a bit further:

Regarding the association of “qualities” with “tones andmodes,” we can consult a manual written about two centuries later,the Micrologus by Guido of Arezzo. Guido writes that, forthe cognoscenti, recognizing the “characters and individualfeatures” of the modal patterns is like distinguishing people ofGreek, Spanish, Latin, German, and French origin from each other. Thus, the“broken leaps” of the authentic deuterus mode, the“voluptuousness” of the plagal tritus, the“garrulousness” of the authentic tetrardus, and the“suavity” of the plagal tetrardus are distinctly recognizable.Guido also writes that this diversity of characters matches the diversemental dispositions among different people, so that one prefers this mode,whereas another prefers that one.