Valery Gergiev's Shostakovich cycle at the Barbican is suddenly hurtling towards its close. The remaining six of the 15 symphonies are to be dispatched in three consecutive evenings by Gergiev's own Mariinsky Theatre Orchestra, fresh, if that's the word, from performing Wagner's Ring over only four days in Cardiff at the weekend. Nobody but Gergiev would attempt such a schedule; few orchestras except the Mariinsky would agree to it.

A few years ago, the Mariinsky string sound was unmistakable. Any violin passage involving fast cascades of notes would sound terrific, because the musicians were hurling themselves at every single one, hitting them together, and with pinpoint accuracy. In this programme those moments of blistering unanimity were elusive.

There is still a Mariinsky sound, and it was in evidence here from the start of the Sixth Symphony, in the richness of the blend of lower woodwinds and lower strings, in the way the cellos and basses dug in deep. Yet something was missing. A sense of a journey, perhaps; the opening movement, with its pensive, Bach-like counterpoint, felt like one long beginning. In the two ensuing scherzos Gergiev turned the corners neatly but kept things at a single level of tension.

The Symphony No 13, Babi Yar, came across better, thanks partly to a stalwart performance of the bass solo by Sergei Alexashkin and sonorous support from the men's chorus. The briefly cacophonous funeral march of the first movement hit hard. The second movement, Humour, was decidedly deadpan, but the third and fourth formed a shapely double slow movement. A plucked passage in the finale proved the strings can still find their old discipline.

It's hard not to conclude that, schedules permitting, this could have been a better performance; that by Gergiev's sky-high standards, audiences are being ever so slightly short-changed.

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