It took Mavis Staples until 2011 to win her first Grammy, for the Jeff Tweedy-produced You Are Not Alone album. She has turned again to the Wilco frontman for One True Vine, which takes the previous album's premise – to introduce Staples to a new crowd by rediscovering her funk/blues roots – and strips things back even further. The mood is sombre, the pace slow-to-mid and Staples means every word she sings. "I get tired and lose my way," she says grimly on Every Step, sounding every minute of her 73 years; backed by Tweedy on acoustic guitar, she's truly mesmerising. Her version of Funkadelic's Can You Get to That doesn't radically mess with the original, but her voice is heavy with portents of punishment to come for financial and spiritual mismanagement. Progressively, though, her tone lightens, and here's where One True Vine relaxes its grip on your attention. While Staples is no less committed on Nick Lowe's strummy, optimistic Far Celestial Shore and the gospel uproar Sow Good Seeds, she's far more impressive when a song gives her something to brood about.