"Prophetic" and "tragic" are the two adjectives most commonly applied to Mahler's Sixth Symphony. Arguably his greatest work and certainly his bleakest, it has been interpreted as containing psychic intimations of imminent private catastrophes (the death of a child, a diagnosis of terminal illness), or as forming a musical preview of the totalitarian disasters of the 20th century.

"Extreme" is a word we might well now add to the list after this anguished performance by Mariss Jansons and the London Symphony Orchestra, which steered the score into the terrain of existential absurdity. This was a reading that uncompromisingly lacked the nobility that goes with genuine tragedy. Jansons presented us with a study of unremitting futility, and it didn't make for easy listening.

Flying in the face of convention and reopening old controversies were essential to Jansons' purpose. For reasons that have never been fully established, Mahler dithered over the order in which the inner movements of the symphony were to be played. Critical consensus places the Scherzo before the Andante. Jansons, however, reversed them, heightening the impact of one crucial aspect of the score: its jolting juxtaposition of moments of voluptuous sweetness with passages expressing nullity and near-revulsion.

He established this violent contrast at the outset of the first movement, hurling out the opening march with the crushing inevitability of a juggernaut, then investing the second subject with sensual delirium. Consequently, the Andante - its orchestral lushness offset by a disturbing melody that never follows the contours you expect - carried intimations of the slow souring of the emotional idyll that forms the first movement's only moment of respite.

The Scherzo, with its broken-backed themes, graceless xylophone clatter and thudding timpani, set the nerves further on edge. The most powerful moment of dislocation derived from the placement of the Scherzo next to the Finale, with the opening theme of the latter whirring upwards out of the gloom as a last vestige of optimism that is about to be crushed.

The playing at the Barbican was tremendous, with a morass of tone colour that swerved from supreme beauty to total rawness, taking in everything in between. Above all, the performance confirmed that this extraordinary work still has the power to shock.