Massimilla Doni

Massimilla Doni, the Duchess Cataneo, has a husband who won’t do his conjugal duty and has encouraged her to find a replacement. So she has grown to love the young Emilio Memmi, Prince of Varese. Unfortunately, he idealises her so much that he is unable to consummate the relationship (although he has no trouble making love to Clara Tinti, a low-born opera singer).
Meanwhile, the Duke Cataneo can only achieve the ultimate pleasure when he hears two voices (or a voice and violin) singing high Cs in unison. When this occurs he ‘can embrace the infinite’ and rolls about on the carpet. So he has trained Clara Tinti to sing.
At the opera house, the tenor, Genovese, can sing beautifully on his own, but brays like an ass when Clara Tinti is on stage. This is because he loves her.
Fortunately, the Duchess’s friend Vendremini and a visiting French doctor find unorthodox cures for these remarkably dysfunctional people.