Columbia subject headings:
Gregorian chants--History and criticism--Congresses.
Improvisation (Music)--Congresses.
Maronite chants--History and criticism--Congresses.
Harvard subject headings:
Gregorian chants--History and criticism--Congresses.
Improvisation (Music)--Congresses.
Maronite chants--History and criticism--Congresses.
Princeton subject headings:
Gregorian chants--History and criticism--Congresses.
Improvisation (Music)--Congresses.
Maronite chants--History and criticism--Congresses.