Another royal appointment for compelling Carosi

The oddest piano I ever saw sits in a corridor in Cairo Opera House. From a distance it seems normal, but when you look at the keyboard you find more keys than you expect. Where conventional pianos subdivide the octave into twelve semitones, this one divides it into 24 microtones. Made in the Thirties, this hybrid beast was to spearhead a campaign which was then being promoted by Egyptian musicians to systematise their "untamed" Oriental music so that it could compete – as they hoped – with the systematised classical music of Europe. The campaign didn't work, and their music remained its splendidly Oriental self, but it did reflect a musical inferiority complex which had been gathering strength ever since Verdi created his Aida as a celebration of the new Cairo Opera House – and of Egyptian history – in 1871.

Not that he took Egyptian history very seriously, because his story is full of anachronisms. It takes place in some nebulous Upper Egypt containing a temple bizarrely dedicated to the Roman god Vulcan; in contrast to the historical pharaohs, who led their armies like warlords, his version of Egypt is ruled by "the King". But dealing as it does with love, patriotism, and the life and death of empires, Aida has a timeless attraction for the politically-minded, whether democrats or tyrants: Mussolini loved it, as did Mrs Thatcher, who made its Triumphal March the one classical item on her list of desert island discs.

Its attraction for opera directors is equally timeless, whether they adopt the traditional elephants-and-pyramids approach, or whether they shun this like the plague. Zandra Rhodes recently made a sub-Hockney stab at it for English National Opera, but her bling-filled Pharaonic parades were more West End than west bank of the Nile. Robert Wilson's 2003 version for Covent Garden transported the action to a slate-blue world of Japanese Noh theatre, where the characters moved, all passion frozen, at a glacial pace.

Next Friday the Royal Opera House will see a revival of the version which David McVicar created last year. Not everybody admires his take on the subject, but it's certainly original, and it doesn't stint on spectacle. For him, this is an opera about "love being violently crushed by a war-based, death-obsessed empire", best exemplified by the young male bodies ritually disembowelled in his luridly-lit temple. His brief to his designers was simple: they could quote from any culture they liked, so long as it wasn't Egypt's. As a result, this show draws on Aztec, Indian, and nomad imagery, as well as on a home-brewed idea of the Pharaohs' ancient kingdom.

For the Italian soprano Micaela Carosi, who as McVicar's Aida will be partnered by Roberto Alagna, this drama happens in "no geographical place, but entirely in the mind", which she says is where it should be. I catch her as she's just finished starring in Madam Butterfly at the Bastille Opera in Paris, and when she's through with the Covent Garden Aida she'll be off to sing Tosca in Guangzhou, followed by another Aida in Verona. She's a very busy lady, though not – as yet – a household name over here.

With a strong accent and rudimentary English grammar, this forceful thirtysomething wears her Roman provenance with pride. And as she tells her story, one senses an unusual determination. Her art-teacher parents encouraged her musical proclivities, but it was her uncle, an operatic bass, who set her on her path: "Whenever he sang in Rome he took me backstage, and there I got a magic perspective" – she mimes people smilingly taking their bow in the limelight, then swearing and coughing their guts out as the curtain falls: "The two faces of the theatre."

Her own first role was a walk-on – or ride-on – as the widow passing in her coach whom Rossini's Figaro hails: "I gave a wave like a queen – all they saw was my graceful hand." When she was eight she joined one of Rome's two main children's choirs, and when she saw Liza Minnelli in New York, New York she wanted to do that too. "I didn't think about opera. It was just the rapport between her and the public – and her red dress. In my room at home I had an orange carpet, and I played all my games on it; it was my stage."

She wore out her vinyl collection listening to Callas and Katia Ricciarelli and started taking singing lessons at 14, forcing her way into a conservatoire precociously early. There she had the luck not to be unhealthily pushed: they didn't destroy her nascent soprano by forcing it, and she graduated as a mezzo. After seven not particularly successful years, "I decided to make a big effort to realise the fruits of my studies. And if I didn't succeed, I would give up completely, and think about doing something else." She enrolled for all the big European singing competitions, and immediately started to win them, starting with Spoleto. Told that Franco Zeffirelli was recruiting for a new Aida, she offered herself, but was told that as he wanted a black singer for the title role, he would give her the off-stage role of the high priestess. But the great Italian tenor Carlo Bergonzi, who was starring, took a shine to her, and battered his director so relentlessly that Zeffirelli finally sacked his black star and instated Carosi in the title role. The new director-singer partnership worked so well that Zeffirelli made her his Aida in a production in the Verona amphitheatre, then imported her into a production of the same opera in New York; meanwhile, she also sang Aida in a production by the film director William Friedkin in Turin. No wonder the role now fits her like a glove.

Zeffirelli saw Aida as being young, innocent, and not knowing much about love. McVicar puts more emphasis on her royal origins, and sees her as maturer, just torn between her love for Radames and her duty to her native land. "In Zeffirelli's arena production you are never alone," says Carosi. "His stage is alive with people and symbols, with things constantly happening. But here the staging is mostly empty. It's very simple, very concentrated, a different kind of drama." Does not it too have symbols? "Yes, but when the priest takes the sacrificial victim's blood and smears it on the warrior's knife, that symbol works powerfully. I have never before seen that moment work – but here it seems completely natural, totally convincing. And I like the fact that I have just one plain dress throughout."

And plain is the word for Carosi's approach to our interview: with no interest in delivering "quotes", she just wants to talk about the work, and about what she considers its "most beautiful page", which is when Aida comes under intense emotional blackmail from her father. "I am tormented by guilt, oppressed by my patriotic duty, and in that scene I focus entirely on the words – 'Padre, a costoro schiava non sono, non maledirmi, non imprecarmi' ['Father, I am not their slave – do not curse or revile me']." That line, she points out, is all legato, with no big leaps, "and I do it quasi parlando – almost speaking – it's so important to make her really implore her father. She will do her duty, even if it kills her. In that moment she becomes fully the princess. In that moment she changes completely." And as Carosi tells it, she changes completely before my eyes, so totally has she internalised her character.

Before she goes to rehearse the climactic final scene, in which she is willingly immured with her lover, I get her take on it: "It's like a mad scene, a catharsis. She is without force, but she has serenity, she smiles because she has honoured her two conflicting loves. She hears the choir's death-chant in the distance... " And again she is inside her character, before stepping outside it to mock her lover Radames's contrasting desperation: "His attitude is just 'Get these fucking rocks off me!' But me, I welcome them."

In view of recent events in Egypt, now is a good time to be reviving this opera anywhere, but when it's next performed in its birthplace, the political reverberations could be intense. The website of Cairo's opera house is currently inactive, but the building is ready and waiting for the democratic dawn. McVicar's bare-all show would offend Muslim sensibilities, but the transfer of a clothed version might make a nice goodwill gesture.

'Aida', Royal Opera House, London WC2 (020 7304 4000) 11 March to 15 April