The rebirth of Vivaldi's lost opera L'oracolo in Messenia has been an extraordinary project - and seeing it performed is an extraordinary experience. Fabio Biondi began from just two versions of Zeno's libretto: Vivaldi's original Venice edit, and his Viennese revision, finished only months before his wretched death in obscure poverty in Vienna in 1741. L'oracolo was always known to be a pasticcio, a tapestry of recycled music selected by Vivaldi – which included not only his own work, but also those of other composers: an accepted technique of his time. Biondi therefore set out to reanimate the Viennese libretto with a relevant choice of arias and recitative by Vivaldi, Hasse and Giacomelli: and his reconstruction is absorbing, entertaining and majestically beautiful.

Like a vast, bejewelled procession through the streets of a Baroque city, L'oracolo in Messenia moves slowly, but constantly fascinates, glittering with vocal ornament and glowing with emotions: rage, lust, greed, aggression, idealism and love, all underscored by some of the most demanding coloratura I have ever heard. Indeed, from a stately, even slow start, this opera becomes one of the most intense performance experiences I have witnessed: quite why remains slightly mysterious. The story, taken from Euripides' lost tragedy Merope, is certainly unique, but has familiar features: a long-lost child returning as avenger, a widow besieged by a powerful but hated suitor, an usurped kingdom, black-hearted henchmen and a kidnapped princess. The slightly static nature of concert performance, moreover, doesn't always allow a drama to feel real. But at the Barbican, Biondi creates a magic mood on stage which draws all of us in to his marvellous experiment; he is not afraid to kiss the hands of his soloists at the end of each act, or pause at the end of an aria to allow the soloist to receive tumultuous applause, acknowledging them quietly with a beaming nod. And so, gradually, a proud momentum and shared sense of purpose builds up on stage, which I can only liken to watching a great rock band, or a vital football match: everyone becomes implicated in the success of this piece, including the audience. And perhaps that is why it makes such an intoxicating spectacle.

Europa Galante, conducted by Fabio Biondi from a 1686 Andrea Guarneri violin, as well as a 1766 Ferdinando Gagliano violin lent by the Salvatore Cicero Foundation in Palermo, make a rich, warm sound with their selection of period instruments. The overture invokes a mood of adventure tempered with reflection; as the opera progresses, the balance between orchestra and singers is largely perfect. In keeping with the general atmosphere of teamwork, it seems particularly fitting that this orchestra is centre stage: we are very much viewing the performance of the whole work, including the instrumental line, not only following a story. Occasionally, the singers interact with the orchestra, Polifonte in particular ironically pretending to conduct at times.

Marianne Beate Kielland is magnificent as Merope, singing with creamy fullness and fabulous range. Kielland acts wholeheartedly and Merope is a treat of a role, greeting her unwanted suitor with the distinctly unpromising words, "Polifonte, I'll be honest with you: I hate you." Soon afterwards, her stratospheric aria inviting the Furies to “strew her marriage bed with vipers” instead of flowers shows Merope brimming with hostility, Kielland injecting adrenalin into the entire work with her wonderful portrayal of outraged anger, while her sudden self-doubt when she almost recognises her son (before ordering his death) is genuinely touching. Magnus Staveland's Polifonte is nicely scheming, almost verging on the camp evil genius, but always sung beautifully with huge reach. Staveland endows Polifonte with a magnificent sense of his own self importance, and a genuine delight in villainy (one of his arias sums up as, "It's fun when you're allowed to kill people").

Franziska Gottwald is smooth and lyrical as Licisco, her sable-toned mezzo a marked contrast to the other female voices, her performance always committed and sincere. Licisco's "Nell'orror di notte oscura" was a particular highlight, coming (like Licisco's other aria, about love) almost as a hidden surprise from a character who turns out to be so much more than a mere factotum. In a similar vein, Julia Lezhneva's Trasimede appears to be a small part, but everything changes with her showstopper "Son qual nave". Lezhneva, until then a demure and self-contained presence on stage, changed the whole atmosphere of the concert hall in one jaw-dropping display of virtuosity which saw her awarded roses mid-performance, to the ecstasy of the crowd. Her amazing dexterity and control over hundreds of rapid notes, the vocal equivalent of a firework display, was simply stunning. Elsewhere, she expressed Trasimede's passionate love for Merope with a sweet sincerity which shows her acting does not disappoint.

Vivica Genaux gives us a vulnerable Epitide, her voice full of expressive colour. Genaux decorates her soaring arabesques of melody with plenty of coloratura, but rather than being otiose, these additions represent Epitide's developing thoughts and decisions, her coloratura serving to deepen her characterisation. Marina de Liso is affecting and lyrical as Epitide’s beloved Elmira, a fiery princess with resolution and power of her own. Rupert Enticknap takes some vocal risks to draw his murderous henchman Anassandro, but is repaid with excellent characterisation.

The general spirit of camaderie, with each soloist relishing their own part and refusing to upstage or be upstaged, overseen by Biondi’s calm and confident delight in his ensemble’s performance, give Europa Galante’s L’oracolo a special intimacy which, alongside the ferocious technical achievements of the cast, make this otherwise ordinary Baroque opera into an unforgettable evening of assured virtuosity.