Columbia subject headings:
Echo--Congresses.
Performance art--Congresses.
Sound in art--Congresses.
Theater--Philosophy--Congresses.
Harvard subject headings:
Echo--Congresses.
Performance art--Congresses.
Sound in art--Congresses.
Theater--Philosophy--Congresses.
Princeton subject headings:
Echo--Congresses.
Performance art--Congresses.
Sound in art--Congresses.
Theater--Philosophy--Congresses.