LSO / Andre Previn Barbican, London
Programme changes are an evil; but they can be a necessary evil. All I ask is that somebody tell us about them. When you are mentally preparing yourself for the sweetly tranquil opening of Copland's Appalachian Spring, the last thing you want is to be hit between the eyes with Bernstein's Candide Overture. Who knows, there may have been people in the Barbican audience on Sunday who thought they were actually hearing Appalachian Spring. Do some sort of trade description laws apply?

Disappointment lasted for more than a couple of seconds. Good as the performance by the LSO under Andre Previn was, Bernstein's brash, breezy curtain-raiser is no substitute for Copland's serene evocation of wide open spaces and the heroic simplicity of the Shaker spirit. And the disappointment continued through the two works that followed - by Previn himself. Honey and Rue is a setting of six poems by Toni Morrison, a lot of it self-consciously mixing warm, friendly harmonies with slightly dissonant vocal writing - we mustn't get too friendly, must we. Well no, some of Morrison's texts touch on dark themes, especially on the sufferings of Black American slaves in the final song "Take My Mother Home". But here the use of spiritual and blues mannerisms, with drum and bass combo (Previn himself vamping or strumming occasional chords at the piano), sounded particularly lame and synthetic, however winningly soprano Harolyn Blackwell sang. It was a mild relief though to discover that Morrison had wished for "a heart that could close like a coat," and not - as the Barbican programme put it - "like a goat."

After this came Previn's Vocalise for wordless soprano and small orchestra. In his notes, Previn more or less admitted that his original version had been self-conscious in its use of dissonance and dislocation. The version we heard was, he told us, "totally straightforward". Bland as it was, the simplicity was welcome, as was the expressive ease and fluency of the vocal writing, which Blackwell seemed to enjoy.

By this stage, however, my heart had closed up like a coat. It was a relief to move on to the second half, and an American work which is rarely heard (in this country at least) but deserves to be better known, William Schuman's Third Symphony, written in 1941. This impressively-wrought work owes a little to Schuman's pioneering teacher, Roy Harris, and to the spirit (if not the example) of Copland. But it has a mind of its own, and an ability to think cogently in long spans. The use of the orchestra is equally impressive; bright brass and subtle woodwind colours, and a strikingly reverberant passage where the cello section strums big chords like an amplified soloist. So, too, is the muscular, unsentimental optimism. One could criticise a composer for writing such determinedly positive music in the year of Pearl Harbour and America's entry to the Second World War. But it equally can be argued that the world owes a lot to the kind of determination to win, expressed so potently in the Third Sympathy's closing pages. Whatever, Schuman's Third Symphony hasn't dated. In this performance it sounded as fresh and determined as ever. We need such sentiments today, too.