Mozart’s first great opera, Idomeneo, is not often performed, and perhaps it’s better that way. It should be seen as a festival work, celebrating qualities that we rarely reflect on, but are of the utmost importance. In his fine essay on the opera, David Cairns writes that it encompasses ‘love, joy, physical and spiritual contentment, stoicism, heroic resolution; the ecstasy of self-sacrifice, the horrors of schizophrenia, the agonising dilemma of a ruler trapped in the consequences of his actions; mass hysteria, panic in the face of an unknown scourge, turning to awe before the yet more terrible reality; the strange...