Every opera is a transgression against itself. Music always ends by both reinforcing and contradicting the verbal text that it tries to set; for music is far more rich in interrelations, far more semantically replete than spoken drama. The thrill is always a mixture of the right thrill and the wrong thrill. The best libretti leave a great deal of room for misunderstanding why a character is moved to sing.

Shakespeare's Romeo and Juliet looks like the ideal play for an opera, full of all sorts of possibilities for transgression: the rebellion of love against authority, the rebellion of giddy poetry against the common prose of domestic arrangements, the rebellion of spontaneity against prefabricated social structure. But these rebellions are largely illusory: Romeo and Juliet become outlaws in one social system, only to become obedient servants of another social system. Romeo and Juliet is a profoundly hemmed-in play, in which every assertion of freedom is in fact a restriction, until finally the space that the lovers can occupy contracts to the size of a vault in a tomb. No completely successful Romantic opera was ever written on this play, partly because Romeo and Juliet, like their parents, are instinctive conformists. Their poetry bears only a superficial resemblance to Romantic poetry; in fact it is written strictly to rule.

Still, the fact that the play's theme is love—love grown huge and intense—has long made it attractive to opera composers.