Columbia subject headings:
Engraving, European--Exhibitions.
Klais, Hans Gerd--Art collections.
Organ (Musical instrument)--Exhibitions.
Harvard subject headings:
Beethoven-Haus (Bonn, Germany)--Exhibitions.
Klais, Hans Gerd--Art collections--Exhibitions.
Musical instruments in art--Exhibitions.
Organ (Musical instrument) in art--Exhibitions.
Organ (Musical instrument)--Construction--History--Exhibitions.
Organ (Musical instrument)--History--Exhibitions.
Princeton subject headings:
Klais, Hans Gerd--Art collections--Exhibitions.
Organ (Musical instrument) in art--Exhibitions.
Organ (Musical instrument)--Construction--History--Exhibitions.
Organ (Musical instrument)--History--Exhibitions.