Bonnie Raitt isn’t kidding when she forewarns that you probably won’t get in a word edgewise when she and Taj Mahal lock into a conversation. “We interview ourselves and occasionally let you guys have a question,’’ she says, laughing.

You can’t blame them, of course. These two have a lot to talk about, from fond memories of their early days in Boston to shared musical influences (blues legends and unsung ’60s singers like Judy Henske and Judy Roderick) to, maybe most of all, their mutual admiration.

After 40 years of friendship, Raitt and Mahal have just launched a new joint tour called BonTaj Roulet, which comes to the Bank of America Pavilion tomorrow. (Tonight’s show at the Cape Cod Melody Tent is sold out.)

Raitt, 59, and Mahal, 67, got their professional starts around here, but their paths never crossed. He was born in Harlem but grew up in Springfield and later attended UMass-Boston and vividly remembers playing at Club 47 (now Club Passim). By the time Raitt arrived in 1967 as a freshman at Radcliffe College, Mahal had cleared out to California, but they eventually met through Dick Waterman, Raitt’s mentor back then. Raitt befriended Mahal when she opened for him at Skidmore College in the early ’70s, and he ended up coproducing her classic 1973 album, “Takin’ My Time.’’

When we spoke last month, Raitt and Mahal hadn’t ironed out the logistics for their tour, aside from exchanging wish lists of songs they’d like to perform together. The show will feature solo sets from each artist, along with a 30-minute closing segment together. Raitt mentions they’re especially proud that they’ve tried to keep ticket prices low in this tough economy, and some proceeds will benefit social causes determined by fans’ feedback at www.bontaj.com.

Following is an edited transcript of our feisty, half-hour conversation that, just as she predicted early on, Raitt and Mahal deftly guided and turned into a history lesson on four decades of playing the blues.

You’ve known each other for a long time, so is it surprising that this is the first time you’ve toured together?

Mahal: Well, both of us have had very busy careers, and that’s just on the music side. And then there’s other things that we’re involved in.

Raitt: Basically, when people say, “How come it took so long?,’’ it’s because we’re both headliners and we have our own albums and bands.

Bonnie, do you remember when you first discovered Taj’s music?

Raitt: Oh, yeah, that first album [1968’s “Taj Mahal’’]. The first two albums to me are still two of my favorite records that stand the test of time. Taj was creating something so fresh and new and still so funky and authentic. To have a young black man carry on the blues tradition and then take it someplace else and tap into such deep stuff from the very beginning – it’s like a one-man party in Taj Mahal’s discography. I was very honored that he agreed to come help me out on my third album.

Taj, what do you remember about Bonnie opening for you at Skidmore?

Mahal: Well, she could play. That was it. She was a musician. See, a lot of people got up there and they appear to the audience [adopting a smug tone] – “Here I am, with my ringlets and my curls and my fingerpicks’’ [Bonnie laughs] – and she didn’t do that. She got up there and she played.

Raitt: Thank you.

Mahal: No, it’s true.

Raitt: Man, I was so nervous, Taj.

Mahal: Yeah, yeah, yeah. You tell all your men that. “Oh, I was so nervous.’’

Raitt: I didn’t even know how to make ’em nervous by then. I do now.

Mahal: I’m sure you do.

Were you starstruck meeting him, Bonnie?

Raitt: You know, to play in front of your heroes. . . . I mean, it’s one thing to play in front of a 65-year-old guy who’s been married for a long time and you’re an acolyte and you look up to him and all that. But, you know, Taj was packin’ some heat. My girlfriends wouldn’t even let me go from my dorm at Radcliffe down to a club. They said, “Man, we don’t even know if we can trust you. You got an exam coming up, girl.’’ So there was that element, too. But [for] Taj I had tremendous respect as a musician, and he was eclectic and he was intelligent. I sensed early on from every interview . . . that he was drawing from such a wide vocabulary and such a deep well. So for me to perform in front of him, I was still sort of new at this and I was nervous and didn’t really like my voice during those early years. I tried to drink and smoke to make myself sound old, and I got pretty good at that part. I couldn’t even stand to listen back to my voice until my mid-30s.

Bonnie, what have you admired about Taj’s evolution as an artist?

Raitt: The breadth of stuff that he’s discovered and his appetite for keeping the music exciting – whether it’s his blues cruises or his forays into every kind of world music – for the last five decades. The evolution was there as a young man, but it’s just gotten richer. He’s like a touchstone for me. I’ll look at where he’s going and go, “Hey, man, you got room for a little redhead on that?’’

Source: © Copyright The Boston Globe