Happy families are all alike, or was it unhappy families? In Richard Strauss’s rapturous final collaboration with Hugo von Hofmannsthal, his finest and most frequent librettist, the big problem seems to be money. A decayed minor aristocrat hopes to repair his fortunes by means of a suitable match for his beautiful elder daughter, Arabella (Julia Kleiter). Meanwhile, to save on frocks, the emotional younger daughter Zdenka (Valentina Farcas) masquerades as Zdenko, a youth. How up to the minute it all seems! Between three plausible, interchangeable rivals in contention for Arabella’s hand, plus a reject who is besties with “Zdenko,” and a charismatic stranger (Josef Wagner) who shows up in the nick of time, the romance gets tricky, but for everyone we care about, there’s a happy ending. Robert Carsen directs; Fabio Luisi conducts. —M.G.