For the past decade or so, Steve Reich has concentrated on music theatre, working with his wife, the video artist Beryl Korot, on refining their fusion of music, speech and images in the video operas The Cave and Three Tales. Large-scale pieces for the concert hall took a back seat in that period and Reich produced just two major instrumental works: City Life (1995) and the Triple Quartet (1998). Now, though, there is another. You Are (Variations) was first performed in the US last autumn and arrived in Britain as the highlight of the Ensemble Modern's sell-out all-Reich programme at the Barbican.

The premiere followed a performance of Tehillim, completed in 1981 and Reich's first text setting since his student days, and there is clearly a family connection between the two works. Both use texts from Hebrew scriptures - four substantial extracts from the psalms in Tehillim, aphoristic phrases alongside an epigram from Wittgenstein in You Are - and both works follow a fast, fast, slow, fast scheme, with the weight falling upon the first section in each case. But You Are visits harmonic regions far outside the range of Reich's earlier work: the level of dissonance rises steadily in the opening section as the series of variations unfolds, constantly reworking the phrase "You are wherever your thoughts are" in tightly bundled canons. They thin out dramatically in the second and third sections before the finale dwells upon the word "Hallelujah".

As always, Reich's sound world - the six voices of Synergy Vocals set against an ensemble including six percussionists and four pianos - as well as the sureness of his harmonic thinking are beguiling. Conducted by Stefan Asbury, the performances of the new piece, as well as of Tehillim and the orchestral Eight Lines, were marvellously assured. But the level of amplification took a bit of adjustment: what seemed generally tactful in Tehillim seemed much cruder in parts of You Are, so that the subtleties of Reich's phenomenal ear for sonority were sometimes swamped.