Columbia subject headings:
Catholic Church--Liturgy--History--Middle Ages, 600-1500--Congresses.
Church music--Congresses.
Music--500-1400--Congresses.
Harvard subject headings:
Catholic Church--Liturgy--History--Middle Ages, 600-1500--Congresses.
Church music--500-1400--Congresses.
Church music--Byzantine Empire--Congresses.
Church music--Catholic Church--500-1400.--Congresses.
Church music--Orthodox Eastern Church--500-1400--Congresses.
Music--500-1400--Congresses.
Princeton subject headings:
Church music--Byzantine Empire--Congresses.
Church music--Catholic Church--500-1400--Congresses.
Church music--France--500-1400--Congresses.
Church music--Orthodox Eastern Church--500-1400--Congresses.