Dr John Ronnie Scott's, London

Crabbed of posture and gnarled of visage, their jaunty caps slouched on the backs of their heads like a trio of very ancient mariners, Dr John's horn section look as if they've been steeped in brine for a generation or so to achieve the necessary distressed patina required for true rhythm and blues authenticity. By way of contrast, Mac Rebennack, alias Dr John the Night Tripper, looks in remarkably good shape considering the depredations of his life over the 40 years or so of his career.

Yes, he may shamble a little slowly to the stage these days, leaning on his trademark voodoo walking cane for support, but the ex-junkie, part- time magus and all-round musical encyclopedia of New Orleans modes is back on top form, singing and playing piano with masterful wit and guile. When he sails into "Mother, Mother" and the old salts of the section interpolate the chorus of "The Peanut Vendor" into the rising swells of the rolling boogie, it is truly R&B heaven.

The band, called the New Island Social and Pleasure Club, is Mac's regular outfit. It plays so tight that it has come out the other side again and sounds almost wantonly loose. The bass and drums set an easy, loping stride, the guitar strokes out the rhythm as if there were all the time in the world, and the punctuating horn stabs don't so much punch as feint and parry, breathily easing the notes out with little fuss or apparent effort.

Like the band, Dr John's vocals go for maximum grace of movement with minimal displacement, his growling whisper of a voice caressing the syllables briefly before spitting them out to fend for themselves. And though the show begins in a fairly low-key vein, the energy is gradually upped until, by the end of the set, even the horn-men are dancing about like the JBs and only the sedentary Mac looks in need of a break.

The old Night Tripper attributes are still in evidence. There are swathes of satin and velvet over the Steinway, the cloth surmounted by a clutch of obscure percussion instruments, but there is also a digital clock, indicating that business is ticking over whatever the level of excitement. On "Walk on Gilded Splinters", Mac even deigns to stand up and strut for a minute or two, clicking his percussive clacker and shaking his booty, though it doesn't really seem as if his heart is in it. No spells were cast, no gopher dust or grisgris hit the stage, but the old gentleman (actually only 55) provided more than enough evidence to show he still has whatever it was he had - in spades. Like any really great performer, Rebennack has created his own standards, and he lives up to them marvellously. He is at Ronnie's until tomorrow, though it's a very hot ticket indeed.

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