Great musicians should sound as impressive playing live as they do on their recordings, and Phillip Henry and Hannah Martin almost succeeded here. This was the launch for their excellent third studio album, Watershed, and an important outing for their new Watershed Band, in which they are joined by bass, percussion and vibraphone.

They played for 40 minutes but then stopped for an interval, apparently because Martin didn’t have her viola with her – a taxi had been sent to pick it up. But the break meant they lost momentum, unfortunate given that they were already having problems matching the subtlety of their lyrics against the demands of the new rhythm section. The story of Foundling would have sounded more effective with gentler and simpler backing.

If they didn’t always do justice to the songwriting on their new album, with its themes of decision and change, the duo compensated with their instrumental work, particularly in the lengthier second half of the gig. Martin sang well, handling most of the vocals while switching between fiddle, viola and banjo; Henry added some remarkable playing on dobro, guitar and harmonica. He explained that he had once lived in a caravan in Devon, perfecting his skills in “making strange noises” and studying the harmonica technique of his hero, Sonny Terry. It clearly paid off. Two of the finest songs (neither on the new album) involved stomping and whooping solo passages in which he managed to sing and play harmonica almost at the same time.

Elsewhere, his harmonica was matched against Martin’s viola for a rousing and angry traditional song The Nailmakers’ Strike, and he showed off his dobro work on a stomping treatment of the new song London. Classy and entertaining, despite the problems, but I’m sure they won’t consider this the best date on their tour.

• At River Cottage, Devon (01297 630302) on 7 October, then touring UK until 2 November