Since Jonas Kaufmann and Anja Harteros, both German, first joined forces in Mozart’s Così fan tutte in 2000, they have made magic together mainly in red-letter revivals of Verdi and other Italianate fare. Their only Wagner match-up to date was Lohengrin in Munich a decade ago, when with their lyricism, poetic nuance, and vocal majesty they swept all before them. This year, they plunge into the erotic maelstrom of Tristan und Isolde, and fans around the world are delirious with anticipation. Kirill Petrenko conducts. —M.G.