The Legend of the Invisible City of Kitezh, Barbican, London

With an audible exhalation of breath, Valery Gergiev laid down the first, expectant chord of Rimsky-Korsakov's 14th opera.

With an audible exhalation of breath, Valery Gergiev laid down the first, expectant chord of Rimsky-Korsakov's 14th opera. Dappled orchestral colours - a rustle of strings, a fragrant oboe, a shyly exquisite tune in the violins - marked our arrival in Rimsky's naively beautiful nature-world. The maiden Fevronia - a "pure soul", a kind of Russian Parsifal - was our eyes and ears. Her view of this forest idyll constitutes one of the most enchanting scenes in all Russian music.

But, enchantment being the key here, this is only the start. In a performance as fine, as inspirational, as wholly authentic as this from the Kirov Opera, you really feel in the presence of a still largely unsung operatic masterpiece. It's a strange, mystic, pantheistic creation, so deeply rooted in Russian folklore that in many respects only musicians and singers brought up in its ways will do. You can see why it might not travel well.

There's a lot of Wagner in the mix, of course, but Rimsky's gentle touch is everywhere, and the brilliance of his orchestral tapestry seems to spring from the pages of some medieval chronicle. Balalaikas are spirited from nowhere for the wedding procession of heroine and hero; the ricochetting of side drum and trumpets lends a fiery brilliance to the ride into battle with the Tartars. The crowd scenes are wonderfully vivid when bolstered with the Kirov's wonderful chorus and peopled with a gallery of solo voices whose character and belief is etched on every phrase.

Gergiev's strength is the way he breathes with this music, the instinctive way he is able to open up space and scent atmosphere in even the plainest passages. His orchestra, anchored from the string bass line-up, read him as if by telepathy. In the central act, where Fevronia's miracle renders Great Kitezh invisible to the enemy, the combination of Gennady Bezzubenkov's authoritative bass and the profundity of a truly orthodox male voice choir invoking the protection of Heaven made a sound that resonated across the ages.

With the Kirov in their own national repertoire, you tend not to think in terms of soloists, but of ensemble. Everybody has and knows their place. No one seeks to shine or upstage. Only in the Kirov could the indisposition of the lead soprano produce an equally accomplished substitution. Tatiana Borodina was just about perfect, open and direct in vocal production and engagingly plain in her phrasing, as befits this "simple orphan". How moving was the moment her words "Breathe deeper, my soul!" brought on the transfiguration of Kitezh from earthly city to heavenly citadel.

Rimsky touches greatness as Fevronia's words are cast as plainchant echoed in solo cello rising to solo violin, endorsed by a solo quartet of voices. It's the gentlest transcendentalism imaginable. As one of Rimsky-Korsakov's contemporaries put it, the composer "meant not to raise the earth to the heavens, but to bring Heaven itself down to earth". With help from the Kirov, he succeeded.