Columbia subject headings:
Counterpoint--History.
Music--500-1400--History.
Vocal music--History.
Harvard subject headings:
Clausulas (Part songs)
Conductus.
Counterpoint--History.
Music--500-1400--History.
Organa.
Vocal music--History.
Princeton subject headings:
Counterpoint--History.
Music--500-1400--History.
Vocal music--History.