Columbia subject headings:
Mensural notation.
Music theory--History--500-1400.
Music--500-1400--History and criticism.
Proportion.
Harvard subject headings:
Mensural notation.
Music theory--History--500-1400.
Music--Philosophy and aesthetics
Pythagoras and Pythagorean school.
Princeton subject headings:
Music--500-1400--History and criticism.
Musical meter and rhythm.
Proportion.