LSO/Boulez, Barbican, London

Bartok wrote one of the most popular orchestral classics of the 20th century in his Concerto for Orchestra, but, according to Pierre Boulez, Bartok's finest orchestral score with solo instrument, apart from the concertos, is The Miraculous Mandarin, a so-called "pantomime" whose scandalous first performance in 1926 resulted in a ban by the mayor of Cologne, Konrad Adenauer. It was also banned in Bartok's native Hungary because of the "unsavoury" nature of the action. Boulez confined himself, in his "Discovery" concert last Wednesday, to demonstrating how the music told the story, rather than probing its symbolism or how it works as music. (There's an interesting chapter that does both in The Bartok Companion, edited by Malcolm Gillies.)

Anyone could have done much the same, though Boulez was in friendly form, and the London Symphony Orchestra sprang, immaculate, into action for each example at the touch of the maestro's button.

A full performance followed, and another the next evening at the end of a programme saturated in early-20th-century riches. Inevitably, after dissection, the complete pantomime – and it was complete, not the concert suite – lost a sense of discovery, became almost mechanical, and after all that talk of its descriptive aspect, you couldn't help feeling neurotic about identifying the events.

How fresh, in comparison, Skriabin's Poem of Ecstasy sounded at the beginning. Some starter! It was beautifully played, light on its feet – its earlier stages like a distillation of the sweetest moments in Wagner's Siegfried, though extended, surely, a bit too far – say, by about five minutes.

Following, Szymanowski's First Violin Concerto felt like a cold bath after a hot one. This, too, is a work, however exquisite, that seems to lose its way and spend a fair time trying to retrieve it, though what one is meant to feel is a suspension of time. There was certainly no fault to be found in the performance, and Christian Tetzlaff, though with the music in front of him, was utterly in command of the solo part and, just briefly, legitimately impatient with the orchestra in one of the early vigorous passages.

Only Webern's Six Orchestral Pieces, in this context, seemed to have not a note too many, with every expressive point right on target. But then, a great deal of music, surely, seeks to justify itself by length.