The Delgados | Union Chapel, London

Since their excellent second LP, Pelloton, two years ago, the Delgados have been in the bizarre position of best but least-lauded act on their Chemikal Underground label. But it seems only to have fired their ambition. For their third LP, The Great Eastern, they've visited upstate New York for the trademark Catskills-psychedelic embellishments of Mercury Rev's producer, Dave Fridmann, and honed their lyrics into an ethic of positive refusal that puts them in British songwriting's front rank. If no one notices this time, they must wonder what more they can do.

Since their excellent second LP, Pelloton, two years ago, the Delgados have been in the bizarre position of best but least-lauded act on their Chemikal Underground label. But it seems only to have fired their ambition. For their third LP, The Great Eastern, they've visited upstate New York for the trademark Catskills-psychedelic embellishments of Mercury Rev's producer, Dave Fridmann, and honed their lyrics into an ethic of positive refusal that puts them in British songwriting's front rank. If no one notices this time, they must wonder what more they can do.

It's perhaps in this general spirit of kitchen-sink ambition that they've hired not only the Union Chapel - fast becoming the indie Albert Hall, with better acoustics - but string and wind sections, all the better to take The Great Eastern's swirling sound to the stage. In practice, it proves a mixed blessing. They open, with Dylanesque perversity, with "Knowing When to Run", a shivering-cold song of a father murdering his young son and burying him. It's a song with a secret, hiding its meaning inside its overwhelming sound, and this difficulty, of fully communicating content in the surge of so many instruments, is one that will last the whole night.

With the moth-woman silhouette of The Great Eastern's cover on a sheet billowing behind them, and the whole band bathed in red light, the spectacle is undeniable. But co-vocalist Emma Pollock is the centre of attention, and of the effort to keep each song's core audible in the thick, semi-orchestral stew - a beautifully decorated cage of strings within which words and pop energy struggle to break free.

Pollock's smallness contrasts with the force she puts into thrashing her guitar through "Witness", and the subtle acerbity of her singing. But the full house merely sits and watches, regardless. When "13 Guiding Principles" is played so hard the bassist sinks to his knees, five people stand to dance. For the encore, Pollock practically has to order us up. The problem, absurdly, is that they've played too precisely, too grandly - they've been too good to succeed. For such persistently under-rewarded overachievers, it's been business as usual.