Columbia subject headings:
Church music--Catholic Church.
Gregorian chants--History and criticism.
Sequences (Music)--History and criticism.
Harvard subject headings:
Church music--Catholic Church--500-1400.
Gregorian chants--History and criticism.
Sequences (Music)--History and criticism.
Princeton subject headings:
Church music--Catholic Church--500-1400.
Gregorian chants--History and criticism.
Sequences (Music)--History and criticism.