Semyon Bychkov's latest concert with the BBC Symphony Orchestra is best described as a thing of very different halves. The works that formed the programme – Martinů's Concerto for Two Pianos and Orchestra, Shostakovich's Leningrad Symphony – were both written during the second world war, but they're poles apart in scope and intent.

Martinů's rarely heard concerto was a product of his long US exile: it gazes towards ravaged Europe as well as ambivalently contemplating the razzle of a new world that is itself also at war. A slow movement of denuded, eerie beauty is flanked by two motoric allegros full of bitter harmonies. Away from the adagio, the scoring is dense and too unvarying to make it a masterpiece. Katia and Marielle Labèque performed it with pungent dexterity. Unusually for Bychkov, who has a reputation for carefully controlling his material, it could have done with more rhythmic crispness.

Bychkov calls the "Leningrad" Symphony "a cry from the heart against death". His mother endured the siege that triggered its composition, and the conductor's claim that the work is simply in his system was borne out by a performance of great integrity and power. His interpretation goes wider than anger and despair, though both emotions coursed through every bar. There was, throughout, a sense of historical and cultural continuity under threat. The opening exposition, before the invasion theme ruins everything, has rarely seemed so perfectly classical in its form. The twisting phrases of the scherzo conjured up damaged 18th-century elegance. The slow movement, evoking ideas of holy Russia in its suggestions of orthodox church music and cantor-like recitatives, was gut-wrenching. It's the best thing I've heard Bychkov do, and one of the greatest performances of the work in recent years.

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