In 2013, as the classical-music world lurched from crisis to crisis, with orchestras on strike and opera companies vanishing into thin air, the bicentennial of the birth of the towering German composer Richard Wagner (1813-1883) offered a brilliant exception to the prevailing gloom. Productions of his operas filled houses from Seattle to Buenos Aires, and the great companies of Europe and the United States vied to present ever grander stagings of the colossal 15-hour cycle Der Ring des Nibelungen. At a time when so many preeminent musical institutions are collapsing into bankruptcy or labor disputes, Wagner is one institution that seems to endure.