LS0 / Midori / Mehta, Barbican Hall, London, ****

It was Midori's party, but an equal draw to the violinist herself was the conductor. Zubin Mehta's London appearances are mostly confined to tours with his regular orchestras, or supporting friends in special events. Since Midori began her career as an 11-year-old protégée of Mehta's, he was clearly the partner of choice for a celebration of her 20 years in the hot spot. Potentially, that could have been frustrating for conductor-watchers, who had only an overture in which to see him on his own. As things turned out, the partnership was as special as the individual talents.

Few are the soloists who give anniversary concerts in their early thirties, and even fewer those who have such a distinctive profile by that age. Quite apart from her skills and her astonishing tonal refinement, Midori is the only front-line artist, in my experience, to put her education and outreach projects at the top of her programme biography, in front of the prestige appearances that her colleagues in this generally narcissistic profession shout about first. The projects are based in America and Asia, and their prominence contrasts with the attitude of her host, the London Symphony Orchestra, which has developed work like this but keeps it well separate from its concerts.

Midori brings some of the attitudes of a chamber-music player to her relationship with the orchestra. Mozart's Third Violin Concerto went at a relaxed pace but was all about quick-spirited responses and interactions with a half-size string section. Extremely subtle shading and inflection took the level down to whispers and half-lights, which would have seemed precious had the phrasing and the whole atmosphere not been so concentrated and intense. For all the quietness, vigour was still a big feature and the main solo display section rose to a robust climax.

Mehta, the consummate opera conductor, supported with the uncanny sense of anticipation that singers treasure. Being a great accompanist is not only about timing but second-guessing the weight of sound and the way to dovetail phrases. With hindsight, the Leonora No 3 overture by Beethoven had been doing much the same in terms of profiling the big peaks and the lesser peaks, all presented with Mehta's usual exact judgment of accents and crescendos at a steady pace, dramatically but unfussily intensified for the ending.

The Elgar concerto brought together the chamber-like intimacy and the clear sense of direction, and gave the work real international class. Local pride is all very well, but Elgar is not only about Englishness, and the Violin Concerto, his most cosmopolitan major work, seems his masterpiece by miles when played like this, with the focus on the big picture. Midori struck a more forceful attitude when appropriate, but it was the fusion of fine detail with fierce concentration – even when the finale went so quiet that it almost evaporated – that extended from the soloist to the orchestra, which took on an unusual delicacy, and transformed the experience of the music.