The gap between the raw-nerve nuances, earthy inflections and rugged bluesiness of Sarah Jane Morris's singing voice and the disarmingly simple Englishness of her announcements ought to throw a spanner in the works. But so completely does she become her singing self that it's like witnessing two women inhabiting the same body. Whatever a jazz singer is, it's hard to put Morris in that category, but her shows at Ronnie Scott's are always models of powerful songwriting, atmospheric ensemble-playing and passionate delivery.

She is preceded by a sharp quartet led by British bassist Geoff Gascoyne, featuring vigorous young saxophonist Ben Castle. Gascoyne's choice of Winter Wonderland was questionable, but he almost rescued it with his strong, muscular bassline and Gareth Williams's consistently fine piano improvising. The standout, though, was a postbop slalom on a devious structure of Dave Holland's, and Castle made a swerving, whooping sax soliloquy out of it.

Morris brought along a former Ronnie Scott sax partner in tenorist Mornington Lockett, who displayed his customary smooth fire. Much of the material is familiar, but Morris unwrapped some new material from a forthcoming album with Marc Ribot. With lines like "It's Jesus I love... but it's the devil I need tonight", she shows no signs of pulling back from the edge.

• Sarah Jane Morris and Geoff Gascoyne's quartet are at Ronnie Scott's, London (020-7439 0747), tonight.