Their back-stories couldn’t differ more. Ruthie Foster grew up within a Texan family of gospel singers, while Jorma Kaukonen lived all over the world including a stint in the Philippines due to his father’s State Department job. Before embarking on her solo music career, Foster developed her chops by performing in a Navy band that did Top 40 and urban music cover songs at armed forces recruiting events. Meanwhile, Kaukonen spent his formative years playing guitar in The Jefferson Airplane for crowds with significantly longer hair and radically different world views than Foster’s pro-military audiences.

But something has drawn the two of them together for a tour titled Guitar Blues with fellow musician Robben Ford: a love of blues music.

In an e-mail interview with Kaukonen, who is also famed for his work in the roots music outfit Hot Tuna, the guitarist explains why the different acts joined forces.

“This tour puts together three artists who spring from the same well but approach the music in a very different way,” he says. “These factors also make it lots of fun when we play together.”

Listening to Foster and Kaukonen’s latest CDs, it’s easy to detect major differences in the way they approach the blues. The Truth According to Ruthie Foster, which came out Feb. 3, has numbers including “Stone Love” and “Dues Paid in Full” that almost reach Shaft levels of funkiness thanks to towering horns and watery guitars. While “I Really Love You” evokes early Bob Marley and the Wailers, “Joy on the Other Side” finds Foster playing front porch country blues with acoustic guitar and tambourine. She also tackles two songs by contemporary acoustic bluesman Eric Bibb: “Love in the Middle” and “Thanks for the Joy.”

Even though the CD, which features a backing band that includes Ford on guitar and famed producer Jim Dickinson on keyboard, explores a range of sounds, Foster says her perspective on life ties the project together. “The Truth According to Ruthie Foster is my outlook on the ups and downs of relationships and politics and how that makes you a rounded person,” she says.

Recorded at Levon Helm of The Band’s Woodstock Studio, Kaukonen’s River of Time is a mostly unplugged, more organic sounding affair featuring six originals along with creative covers like a mandolin-heavy take on Rev. Gary Davis’ “There’s a Bright Side Somewhere” and a version of Merle Haggard’s “More Than My Old Guitar” with an all-star band that includes Kaukonen, Helm, Bob Dylan’s multi-instrumentalist Larry Campbell and mandolin veteran Barry Mitterhoff. Much of the release highlights the similarities between country blues and bluegrass.

While Kaukonen’s covers are inspired, his originals on River of Time, released in February, shine more brightly. “Cracks in the Finish” is a masterful little pop song with light acoustic blues riffs, and the title track finds the 69-year-old musician taking an unflinching look at mortality with lines including: “The river flows/ It’s just begun/ My daughter follows/ And my son/ My times ends/ I rest on land/ While I slumber/ They’ll still stand.”

Kaukonen says that Helm’s low-key environment was crucial to River of Time’s creation. “It was creative, organic and relaxed in a way that did not interfere with the professionalism of the guys I was working with,” he says.

When it comes to the blues, both Kaukonen and Foster discovered the music at a young age. Foster recalls her parents turning her on to key artists. “My mom was a big Sam Cooke fan,” she says. “My dad loved Lightnin’ Hopkins, Muddy Waters.”

After starting to play the guitar and piano, Foster says she began crafting her own songs at 12. “They were tunes that were simple,” she says. “I wrote kids songs too, because I was a babysitter at the time.”

Kaukonen remembers when roots music was “on the radio and everywhere around you” while growing up. The sound immediately appealed to the young Kaukonen, because of “the raw truth of the content – real people, real situations, and of course the sound was infectiously cool.”

The longtime musician also believes there is a simple reason why the music form still resonates with people. “Truth, groove and reality my friend,” he says simply.

Foster says that the blues and roots music are the building blocks of popular music. “It gets to the bare essence of getting a message across,” she says. “I don’t think we would have the people we saw on the Grammys without roots music.”

It’s a style of music that Foster will always build from during her career. “It’s almost like prayer to me, bringing down everything to where it starts,” she says. “It’s the roots.”

JORMA KAUKONEN AND RUTHIE FOSTER play with Robben Ford 8pm Thursday, Feb 26, at the Golden State Theatre, 417 Alvarado St., Monterey. $20-$45. 372-3800.