Of Richard Strauss’ 15 completed operas, his last opus “Capriccio” is arguably the most abstruse. For a start, it isn’t even called an opera but a “Conversation Piece for Music.” Many Strauss scholars are baffled by this highly cerebral, seemingly escapist bagatelle composed in the midst of the mayhem of World War II. It was as if Strauss and librettist {…}