Even Electra, so often seen as peri­pheral, if musically magnificent, has a parallel history, the reason for her asylum in Crete — a history barely mentioned in the ­opera, but looming over it. Electra has a whole series of skeletons in the cupboard: her sister Iphi­genia sacrificed by her father, her father murdered by her mother and her lover, she herself complicit in the murder of her mother. The same theme is reiterated again and again in music of fury, emptiness, pathos and desperation.

Mozart’s own relationship with his father was very much in his mind in the years leading up to the composition of Idomeneo. It was while he was in Paris in 1778, researching librettos for a new opera, that his mother died. Mozart was, for the first time, a lone adult, ­responsible for himself. The relationship with his father, in Salzburg, entered a crucial phase resulting in a semi-estrangement. The dynamics of self-sacrifice — the son for the ­father, the father for the son — which were part of a child prodigy’s existence (and Mozart had been the great child prodigy of the age), may not have been at the front of Mozart’s mind, and may not account for the choice of such a personally appropriate libretto. The choice was that of the court at Munich, although the musicologist Daniel Heartz has argued that Mozart may have found the 1712 Danchet original in Paris.

Regardless of this, it cannot but be the case that these family concerns inform and infuse the emotional aesthetic of this very great ­opera.

In the summer of 1783, during a visit of Wolfgang and his wife Constanze to Salzburg, the Mozart family sang through the great quartet from the third act of Idomeneo, in which Idamante resolves to leave his father, “Andro ramingo e solo”. Mozart would have sung Idamante; his wife Ilia; his sister Nannerl, Electra; his father Leopold, Idomeneo. Mozart ran out of the room in tears.