The Pierces, Union Chapel, London

What is it about siblings singing together? Sisters Allison and Catherine Pierce follow in a tradition that includes The Proclaimers, The Everly Brothers and The Unthanks, as singers whose voices blend together with apparent ease thanks (probably) to genetic closeness.

This pair of midthirties gals from Birmingham, Alabama seem thoroughly at home at the beautiful Union Chapel, which is still a working church, tonight. "It's so good to see you in the Lord's house," Catherine gushes. "Is this music appropriate for the Lord? All music is, he doesn't mind."

Both sisters dress in long, flowing frocks; blonde Catherine in bridal white and brunette Allison in black. The product of hippie parents, their loyalty to old-school country music and Americana shines through, but during a set that consisted mostly of material from their new album, You & I, they produce a rockier, more polished sound than of old.

You & I, their fourth studio album, was produced by Coldplay bassist Guy Berryman. The sisters credit Berryman with "saving them from extinction" after a decade of trying, but failing, to make it. Berryman made them his first project as producer, invited them to support Coldplay and helped them to some much-needed commercial success, with You & I peaking at number four in the UK album charts last year.

Starting with a cover of Depeche Mode's "Enjoy the Silence", the singers' change of direction from traditional folk heartbreak, to a funkier, more highly produced sound was clear. But luckily their meaty harmonising still cuts a punch, particularly on "Love You More" and the excellent "It Will Not Be Forgotten".

They played "Sticks and Stones" from Thirteen Tales of Love and Revenge. Despite being a mysterious, Gypsy beat, story-teller of a track, it is a reminder of why their lovelorn foot-tapping style didn't quite work for a wider audience. Another low point was a cover of Nirvana's "Come As You Are", which started badly with a tambourine beat mix-up, before being disappointingly dirge-like and screechy. But their take on Paul Simon's "Kathy's Song" was much more pleasing.

Sisterly rivalry does show itself. Catherine dominates the vocals and the spotlight in her bright white dress. Their spoken voices are so similar it is sometimes hard to tell which one is speaking. Swaying, shaking tambourines and playing acoustic guitar they remain old-fashioned folkies despite Berryman's influence. Finishing with four encores, including "Boring", it was unclear which direction they would go in next.