BY RAMSAY PENNYPACKER

For all her hits and Grammy awards, Bonnie Raitt is still, at heart, a blues singer. In her youth, she honed her craft working with such genre icons as Sippie Wallace and Mississippi Fed MacDowell, and while her more recent material might veer towards the middle of the road, her voice has never lost that raw emotion that gives even her smoothest productions a refreshing honesty.

 All she's needed is the right reason to bring those roots back to the surface. And in Taj Mahal she's found the perfect catalyst.

 He's been playing the blues for 40 years, upholding the tradition while placing it in a larger context of soul, reggae and world beat. He brought a note of authenticity to the Rolling Stones' Rock N Roll Circus and opened up a new audience for the form by recasting pop tunes like the Monkees' "Take A Giant Step" in a straight blues setting.

 Mahal also gave Raitt some of her earliest exposure as his opening act in 1970 and co-produced her third album, Takin' My Time, in 1973.

 All this makes their first collaborative tour, pithily titled The BonTaj Roulet, a tantalizing prospect. A spin on the old Cajun phrase Laissez le bon temps roulet ("Let the good times roll"), the show's name certainly offers truth in advertising. On the tour's second date, Mahal got things off to a strong start with a tight yet relaxed set that touched on everything from classics from his own catalog ("Honey Bee," "Further On Down The Road") to the New Orleans R&B of "Hello Josephine," to an intriguing Latin jazz take on Horace Silver's "Senor Blues."

Compared to this, Raitt's performance seemed somewhat tepid as she worked her way through several numbers of the sleek AOR material that's her current -- and lucrative -- stock in trade. Things slipped neatly into focus, however, on a powerhouse cover of the Mabel John Memphis soul classic "Your Good Thing (Is About To End)." Soon Raitt brought out Taj for what she termed "a blues summit" that saw the two old friends trading acoustic licks on a satisfying slice of country blues standards.

Mahal left after adding piano to the gritty "Mean Old World" but Raitt had been transformed. The rest of her set was filled with the aching passion, the masterful control and the remarkably tasty slide work that has always defined her sound. Nowhere was her command more evident than on signature ballads like "Angel From Montgomery" and "I Can't Make You Love Me" where she reinterpreted the melodies and phrasing with the assurance of a jazz diva.

Ultimately, the blues ruled the night as the concert ended with Mahal and his entire band joining Raitt and her musicians for a long, loose jam session. Spontaneity was the key and some moments were pretty rough. But barnburners like "She Caught The Katy" and the Raitt rarity "Calypso Rose" from Takin' My Time proved the perfect channels for the joyous energy pouring off the stage.

The whole show sent people home with an afterglow -- the kind of warm, organic vibe that used to be a hallmark of rock. And if, as Raitt suggested at one point, The BonTaj Roulet might become an annual tour, that feeling should be around for many years to come.