Royal Concertgebouw Orchestra / Gatti, Royal Festival Hall, London

Two pop classics; two very different results. With his heavy-set looks and self-contained, unsmiling manner, the violinist Vadim Repin looks like a man who means business. He plays the Mendelssohn Concerto a little like that fabulously well, but without what one might call a personal level of engagement. It's one of music's great mysteries that a performance that essentially makes all the right noises, and does so with all due diligence and brilliance, can ultimately say nothing.

With Repin, it's very much a question of attitude. Here's a highly objective musician who strives to get out of the way, to present what is written in a no-frills, no-nonsense manner. The musicianship is beyond question, the technical prowess second to none but the phrasing does not entice or smile, and in a piece like the Mendelssohn, where familiarity can, at very least, breed complacency, I for one should like to have known what Repin was feeling as he played it.

Daniele Gatti, on the other hand, leaves you in absolutely no doubt what the music in hand means to him. In Schumann's Manfred Overture, he and the Royal Concertgebouw took patience and concentration to a new level: tentative beginnings striving for trail-blazing immortality. But it was Tchaikovsky's fatalistically Byronic Fifth Symphony that really blew the lid off proceedings. I can probably count on one hand the live performances of this much-played piece that have shaken and stirred me to this extent.

Gripping and audacious in its extremes of tempo and rubato, volatile in its singing spontaneity, it was the kind of performance that hitherto only the Russian musical hierarchy conductors such as Evgeny Mravinsky were allowed to get away with. Gatti is Italian, but stylistically he assumed a Russian soul. He took liberties, plenty of them, but always at the service of the work's emotional dramaturgy.

The playing was thrilling. The first horn made an aria of his great solo in the slow movement, the first oboe and sumptuous first bassoon were equally operatic. But it was Gatti who shaped and motivated their work with such uninhibited and passionate endeavour. He has a high international profile, but I still think he's the most underrated conductor on the planet.