It's rare when a concert opens up a whole new repertoire with such conviction and power that you feel you want to hear everything the composer wrote, but Valery Gergiev's concert performance of Rimsky-Korsakov's opera Mlada, with his Mariinsky Theatre forces, was just such an experience. Strictly speaking, Mlada isn't an opera at all, but a "magic opera-ballet", a hybrid form that means that for all the brilliance of the vocal soloists, there were long stretches of purely orchestral music, dances describing peasant fairs, pagan temples and supernatural seductions. The story is based on Russian myth: the beautiful Mlada has been murdered by Voyslava and her father, Prince Mstivoy. Prince Yaromir, Mlada's fiance, avenges her death - after dealing with denizens of the Russian underworld - by killing Voyslava, only to die himself as the whole town is magically flooded.

It's a story that inspires some of Rimsky's wildest and most adventurous orchestral writing. The third act, with its long evocation of the mystical Mount Triglav and the Kingdom of the Shadows, had some shockingly vivid orchestral effects, including a long passage for two panpipes, as Yaromir falls for the charms of a vision of Cleopatra. Rimsky had just heard Wagner's Ring cycle for the first time when he wrote Mlada in 1890, and there were moments of Wagnerian colour, such as the cascading arpeggios - like the opening of Das Rheingold in reverse - at the start of the third act. But even more striking was the music Rimsky wrote to dramatise the evil Kashchei, also in the third act. This is the same villain who steals the show in Stravinsky's ballet The Firebird, and it turns out that Stravinsky stole his musical ideas for his Kashchei from Rimsky: in Mlada, there are the same harmonies, orchestration, and even some of the same rhythms as in Stravinsky's famous Infernal Dance.

Whether in the long sequence of dances in the second act, or the overwhelming immolation of the fourth act, Gergiev and the Mariinsky were magnificent in their creation of dramatic energy, and the soloists were uniformly excellent: a full-voiced Yaromir from Avgust Amonov, Mlada Khudoley's heartbroken Voyslava, and Mikhail Petrenko's corrupt Mstivoy. In other hands, Rimsky's music could have sounded merely exotic, but Gergiev revealed Mlada as one of the most fascinating of all late 19th-century operas.