There are those who believe Siegfried, the third installment of Wagner’s “Ring” cycle, to be the greatest of the four. As commentators seldom fail to mention, having completed the magical second act (with its diaphanous Forest Murmurs, the jubilant Woodbird, and the thunderous battle with the dragon), Wagner abandoned the score for 12 years, during which he tossed off Tristan und Isolde and Die Meistersinger von Nürnberg. With those massive trifles out of the way, Wagner returned to the final act of Siegfried with a second wind that takes the breath away. Torsten Kerl, at his capable best one of the most thrilling heldentenors on the scene today, takes the superhuman title role. Vladimir Jurowski conducts. Siegfried runs some five hours; the 3:00 p.m. start time is a kindness. —M.G.