MUSIC / A wild eye on the future: Robert Cowan hears Simon Rattle and the CBSO perform Mahler, Berg and Shostakovich at the Proms

Mahler and his successors,' provided the unwritten subtext for Monday's Prom, with Alban Berg's gnomic Altenberg songs serving as a narrow bridge between the anguished scream of Mahler's last completed Adagio and the perennial shock of Shostakovich's outrageous Fourth Symphony.

Heather Harper re-enacted Altenberg's cryptic texts as if she'd written them herself, conspiring with Berg and Simon Rattle to mirror the suggested uneasy peace beyond snowstorms, thunder-showers or the edge of the world. Her bearing was regal, her musicianship profound, and her voice amazingly well-preserved. Rattle himself shaded Berg's subtle orchestral backdrop as on a nerve's edge, whether in the first song's delicately motorised opening, or the fourth's more desolate reaches (with Harper, a particularly affecting protagonist), or the fifth's unexpected rage.

Berg's score is full of exquisite incident, the sort that Rattle surveys like an excited jeweller confronted with a newly discovered treasure- trove: detail was legion and everything 'told' with perfect clarity. But then it had followed the expansive Adagio from Mahler's Tenth, an odd choice given Rattle's well-known advocacy of Deryck Cooke's 'performing version' of the whole work - it too was impeccably designed, with vivid accents, finely traced hairpin dynamics, rapt pianissimos and impressive mobility. And yet it all seemed rather too carefully calculated; a busy, keenly observed traversal that somehow eluded the heart of the matter - Mahler after therapy, perhaps, remembering the trappings of his old self without daring to relive them.

No, the evening's best Mahler was in Shostakovich's long-suppressed Fourth, a hybrid monster with one wild eye on the future, and the other fixed on the recent past - and on Mahler in particular. The Mahlerian axis is reflected in chirpy bird-calls, cafe-style waltzes, a mock-funeral march, raging climaxes and a generous time-span. And when, roughly two-thirds through the first movement, the strings suddenly plummeted into fugal frenzy, the crowded Albert Hall Arena seemed tensed almost to the point of revolution.

Even the stalls weren't spared: one man was so riveted, he grasped tight to the edges of his seat. Thereafter, the symphony's lighter moments elicited smiles galore, especially from a young female violinist in the orchestra, who swayed blissfully to the lilting rhythm of the finale's charming little waltz tune. But the overriding impression was of harnessed terror and a restless stream of invention crammed full of anticipatory references to later works - to Shostakovich's Fifth and Fifteenth in particular.

The depth of Rattle's insight and the corresponding involvement of his orchestra were awe-inspiring, and if the ultimate destiny of great art is to change you, then I rather suspect that Monday's performance of Shostakovich's Fourth achieved its ends.

The Symphony's final nightmare sequence, with its quietly pulsing basses, baleful winds, and distanfly pealing celesta, was the most telling of all.

The entire audience seemed fazed, perplexed, even a little unnerved. And after the final notes had sounded, the ensuing silence was broken only when - some moments later - Rattle lowered his baton and a grateful storm of applause broke loose. We were all greatly relieved; it was just a bad dream.