LSO/Gergiev, Barbican, London <!-- none onestar twostar threestar fourstar fivestar -->

Dignity and impudence? Beauty and the Beast? One groped for some handle on this unlikely juxtaposition of symphonies: Mozart's No 36 in C major, K425 ("Linz") and Shostakovich's No 4 in C minor, Op 43. True, they have the same keynote; their composers are anniversary boys. But musically...?

On the one hand, we had Mozart at his most elegant, lively and charming. And what we heard from a largish line-up of the London Symphony Orchestra was suave enough in general phrasing, if also a little heavy in sound and drive.

Could more attention have been paid to the shaping of Mozart's vital inner-part writing? Was there just a suspicion of autocue? Gergiev certainly appeared unusually withdrawn. Doubtless he was preoccupied by the ordeal to come.

For, on the other hand, we had what can only be called an enormity. To describe the 30-year-old Shostakovich's most extravagantly scored symphony as sounding like Mahler at his most rustically lumpen, distorted by Prokofiev at his most capriciously grotesque and rescored by Varèse at his most searingly mechanistic, is only the start of it.

More bemusing still are its unaccountable lurches between frenzied energy and numb stasis, high jinks and horrors, climaxes well beyond the pain threshold of the audience, let alone the poor players, and that awesome, frozen emptiness into which it finally dissolves. What does it all mean?

Not what Stalin could have possibly wanted to hear in 1936, at any rate, and Shostakovich's withdrawal of the score and re-emergence with the ostensibly more traditional Fifth Symphony may have been a life-saver. But could he have gone any further down the path of the Fourth, anyway? It is difficult to imagine, even after a reading that surely came the closest to conjuring a sense of consequentiality out of this sprawling score that London has heard yet.

Again, Gergiev seemed restrained of gesture for him, but this was the restraint of concentration, to which the virtuosi of the LSO responded with a steely exactitude in the "iron foundry" passages, and a hushed intentness in the sparser textures, so that when the all-out climaxes came, they seemed the more unbridled.

If the meaning of it all remained as enigmatic as ever, there was no doubt from the minute-long silence with which the capacity audience greeted the work's final fading, that it had all seemed intensely meaningful.