Columbia subject headings:
Music theory--History--500-1400.
Music--500-1400--History and criticism.
Harvard subject headings:
Music theory--History--15th century.
Music theory--History--500-1400.
Music theory--Medieval, 400-1500.
Music--500-1400--History and criticism
Princeton subject headings:
Music theory--History--500-1400.
Music--500-1400--History and criticism.