Strange but true: blues guitarists Bonnie Raitt and Taj Mahal, longtime admirers of each other, have never toured together. Until now. *** ***The road warriors, who have kept the blues alive for decades, will join forces in August on a 30-date U.S. tour with an unusual fan-driven charity element. They will each perform separately with their own bands, and then take the stage together for a blues jam.*** ***The "BonTaj Roulet" tour of amphitheaters, casinos and wineries begins on Aug 6. in Williamsport, Pa., and wraps on Sept. 25 in Rancho Mirage, Calif.*** ***"We've been like ships passing in the night," said Taj Mahal, who co-produced Raitt's third album, 1973's "Takin' My Time."*** ***"I watched a lot of the new generation coming up back then. She just got right in there and stomped it down -- she took it from where it was really being done."*** ***For her part, Raitt praised Taj Mahal for "pushing the blues into new territory, digging into his own African and Caribbean roots, collaborating with African and world music as far back as the '70s."*** ***Tickets will be priced between about $35 and $85. Raitt and Taj Mahal hope to set aside $1 per ticket for their BonTaj Collective Action Fund, with an online vote by concertgoers at (http://www.bontaj.com/thecollective) determining how the funds are distributed. The designated organizations focus on energy, the environment, human rights, and music education. Additional funds will also be raised by VIP ticket packages.