Quite possibly, the Vienna State Opera is the only house in the world that could spin through Wagner’s four-part “Ring” cycle just once per season without flying by the seat of the pants. The so-so production by Sven-Eric Bechtolf has been in place for years, but for A-list maestros, the company has a revolving door: for some years, each “Ring” has had a new one. What makes this possible is the incomparable experience and flexibility of the orchestra in the pit: the Vienna Philharmonic. This year, Ádám Fischer, on the cusp of elder-statesman status, does the honors on the podium. As is usual, the cast consists of top-notch artists at the peak of their form. Tomas Konieczny, who in his Met debut last year blew audiences away as the dwarf Alberich, the epic’s conniving underdog, takes on Alberich’s glamorous counterpart Wotan, chieftain of the gods, occasionally referred in the dialogue as “the Alberich of light.” Not many bass-baritones attempt both parts, but Konieczny is in demand for both. “Wotan is more interesting, and much easier to sing,” he told the New York Times last year. “Alberich is the way to contemporary music, and it’s not always good for the voice.” As it happens, Vienna’s Alberich this time around is the unflappable Scottish-American Leigh Melrose, from whom the daunting likes of Ligeti, Kurtág, Birtwistle, Neuwirth, and Zimmermann are his daily bread and butter. —M.G.