Norma expresses the public world of Roman imperial rule and resistance to it, combines these with individual, private emotion, and finally unites them all. It is both grand opera and domestic drama. For the latter, Bellini writes music that articulates rather than merely expresses, or – as is sometimes the case in opera – obscures, the libretto. In ensuring the text is heard with such clarity – to the extent, at times, of seeming to reign in the accompaniment – Bellini anticipated Wagner, and was praised by him.

The opera’s heart is Norma’s love for Pollione. In fact, the opera is about three victims of love; or six, if one counts Norma and Pollione’s two children, and Norma’s father, the Druid high priest.

For love of Pollione (the Roman pro-consul of Gaul), Norma (a Druid high priestess) suppresses her own people’s struggle against liberation from Roman oppression, and blasphemes her own religion. The latter she does by defiling herself as a virgin priestess, and by celebrating the sacred rite of the mistletoe (‘Casta Diva’) to what we later discover is the music that accompanies her love of Pollione. With painful irony we experience this when another Druid priestess, Adalgisa, tells Norma of her own love, while Norma is herself reliving hers (‘Oh, rimembrenza!’), when we already know that Pollione is also Adalgisa’s lover.

It is important for Pollione to be played by a singer who can act, as well as sing, the part. He is a passionate man capable of eliciting the love of a Norma and of an Adalgisa. This makes him impressive, if not sympathetic. That he transfers his affection from one woman to another is treated, in Felice Romani’s libretto, as morally critical, but not unnatural.

If Pollione is seen as a mere ‘love-rat’ – say, a Pinkerton – then the singer of the role has failed, because his music in Act Two expresses his heroic and ultimately noble status. When Norma offers to save his life if he gives up Adalgisa (‘In mia man affin tu sei’), he responds determinedly and gloriously, ‘No; si vil non sono’ (‘No; I’m not such a coward’), and refuses all chances of escaping death – what’s more, a death according to the Druid religion which he despises as barbaric – alongside Norma, the ‘sublime donna’ for whom he rediscovers his great love.

In the profound lyricism and melody of Bellini’s music, real time often seems suspended in favour of emotional time. Such an effect, and the distinctive articulation of the libretto at crucial moments, makes it no surprise to learn that Wagner was a great admirer of Norma. He conducted it several times in Riga in 1837, and again in Zurich in 1850. He wrote enthusiastically about it, and even composed an alternative aria for Oroveso, Norma’s father, the Druid high priest, an apparently powerful but impotent character, who could even be the faintest pencil sketch for Wotan.

That the domestic drama, involving two women who love the same man, is treated with such realism, in the imperial setting of Druid Gaul under Roman occupation, enhances the unity of the work’s public and private aspects. At the opera’s climax, complete with Greek tragic chorus, the private dimension is further strengthened by the moving involvement of Oroveso and the fate of Norma’s children, so that the crescendo that concludes this Gesamtkunstwerk is by no means only musical.

‘No one,’ wrote the great music critic and Mozart biographer Alfred Einstein, ‘knows what music is who does not come away from Norma filled to overflowing with the last pages of this act.’