“Mai più” (never again): the words are burned into your heart at the end of Leoncavallo’s Zazà, as our heroine finally comes to terms with the fact that the love of her life is lost for ever. The story is a commonplace – it becomes clear in the course of the opera that Zazà’s lover Milio is already married to a wife whom he has no intention of leaving – but Leoncavallo’s words and music are superbly effective in making us live through Zazà’s delight and despair. In Opera Rara’s concert staging at the Barbican last night, Ermonela Jaho produced a magnificent piece of acting to make us believe in every moment.

Jaho threw herself into the role. When she was happy and flirtatious, we smiled with her. When coping with the neuroses of her alcoholic mother, we felt the exasperation. And in every slow step of destruction of the love affair, we stepped beside her, gripped by her facial expressions, gestures and, most of all, the way in which she inflected meaning into her voice. There were lapses in intonation, especially when she was pushing the voice hard, but in such a dramatic portrayal, technical imperfections were forgivable.

Harder to forgive was the poor balance between orchestra and singers. The first act is a sprawling affair – a sort of Adriana Lecouvreur on steroids – in which all hell is breaking loose backstage at a music hall. Leoncavallo’s score is full and rich (this is identifiably the composer of Pagliacci) and Zazà has a generous dose of pure musical beauty and profusion of orchestral colour. Sadly, though, conductor Maurizio Benini seemed to make no concessions to the fact that he had no orchestra pit, with singers in a thin line along the front of the stage. With the BBC Symphony Orchestra in full cry, much of the singing was submerged completely, at least from where I was sitting close to the right hand end of the stage.

I’m not sure what the “concert staging” was meant to achieve: almost everyone was in evening dress, not in costume, there were few props, singers were using scores on music stands and Jaho was the only one who was making a serious effort to act her role. The non-singing role of Totò, Milio’s daughter, was spoken well enough by Julia Ferri, but amplified oddly. I would have preferred a straight concert performance in which the lights were on and I could follow a libretto: in Act I, I found it near-impossible even to know which character was which.

Things came to life in Act II, as Zazà’s singing partner and former lover Cascart finds himself forced to tell her about Milio’s double life. Stephen Gaertner gave us a rich baritone that was filled with nuance as he negotiates Cascart’s mixed feelings of enduring love, business interests and true friendship. Gaertner expressed all of this while singing his duets with Jaho beautifully; he was also the one singer consistently capable of being heard above the orchestra.

From then on, Leoncavallo leads us step by step through the extinction of Zazà’s hopes of everlasting love. Act III, in which her understanding moves from “he has a mistress” to “he has a wife” to “he has a wife and child” to “he has a wife and child and he’s not leaving them”, was riveting and painful.

As Milio, Riccardo Massi made the most of his vocal assets (strength, clarity, good phrasing and intonation) without overcoming a rather closed timbre and limited acting. His big moment is an aria at the beginning of Act IV in which he bemoans the impossibility of his amorous entanglement. Massi sang it well and was an effective partner for Jaho in the depiction of their break-up which forms the rest of the act. Amongst the smaller roles, Nicky Spence impressed as the impresario Courtois, and special mention needs to go to Rebecca Lodge, who made a thoroughly decent fist of the role of Zazà’s mother Anaide, having been given just 24 hours to learn the role after a throat infection caused Patricia Bardon to withdraw.

The name Opera Rara tells you what you need to know: this is a company whose mission is to excavate opera scores which they feel have been unjustly languishing in drawers and to record them and bring them onto the stage. In spite of the not insignificant problems in last night’s performance, Opera Rara have utterly convinced me that Zazà is a work that I want to see again. Mission accomplished.