Columbia subject headings:
Harvard subject headings:
Dramatic music--History and criticism--Congresses.
Musical theater--History and criticism--Congresses.
Musical theater--Italy--History and criticism--Congresses.
Opera--Congresses
Opera--Italy--Congresses.
Princeton subject headings:
Musical theater--18th century--Dramaturgy--Congresses.
Opera--18th century--Dramaturgy--Congresses.
Operas--Stories, plots, etc.
Oratorio--18th century--Dramaturgy--Congresses.