This was an intriguing double bill of very different young female singer-songwriters, all impressive multi-instrumentalists. The headliners, from Atlanta, Georgia, were once two-thirds of the celebrated bluegrass and "progressive acoustic" band the Lovell Sisters; but now they are no longer working with elder sister Jessica, they call themselves Larkin Poe, after a great-great-great grandfather related to Edgar Allan Poe.

Rebecca Lovell plays electric guitar, her sister Megan slide guitar, and on this occasion they were backed by bass and drums for a set dominated by blues rock. Their impressively slick and apparently effortless vocal and instrumental work was aided by a batch of original songs – many touching on their troubled family history – and by Rebecca's contagious enthusiasm.

But there were suggestions that they are capable of far more. Rebecca switched to mandolin for a powerful, brooding treatment of the spiritual Wade in the Water, their best song of the night. She moved to fiddle for a romping reminder of her country roots, then it was back to efficient – if more predictable – electric guitar duets on bluesy songs, such as Jailbreak.

Georgia Ruth, who opened, was even more impressive. She has a pure, thoughtful voice, sounding at times like a contemporary Welsh answer to Sandy Denny, and sat to accompany herself on the harp and then the reed organ, surrounded by a three-piece electric band. She started with a slow self-composed love song, Mapping, followed by the melancholy, harmonica-backed American folk song Old Blue. Then she unleashed her band for the upbeat, chugging Week of Pines, with harp and electric guitar working remarkably well together; before switching direction yet again, with the sturdy and melodic Welsh-language sea shanty, Codi Angor.

On this showing, she's one of the British folk discoveries of the year.

• Larkin Poe are at the Cambridge folk festival from 25 to 26 July.

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