Rock, roots, folk, blues . . . one's just as good, just as vital as the other to Ben Harper. Jim Carroll talks to a giant talent who has never quite become a household name

Ben Harper has played 112 shows so far this year. That's about two shows every three days for him, his lap slide guitar and his band. He'll have added another half dozen by the time he plays Oxegen - his first Irish gig since a legendary Dublin show in 1999. The way Harper's going, he may well beat his 2000 tally, when he went on stage 159 times. It really is all about taking the long road around.

Despite the lengthy tours, best-selling records, all-star collaborations and regular haul of Grammy awards, Harper remains a bit of an invisible man to most music fans. While the freewheeling blend of roots, rock, blues and folk that has always been his patch remains an unfashionable commodity, there's also a sense that Harper is happy to stay where he is and let people come to him. If they like the records and the shows, that will do for him.

After all, a higher profile would probably involve spending more time on the promotional trail, and that would not do for this reluctant interviewee. Sure, Harper's a polite and friendly individual, but every answer he gives is guarded and cautious. He says at one stage that he doesn't want to give too much away: "I have to keep something for myself, you know."

But just ask him why he's stayed on the road for 10 years and if he still enjoys it, and then he starts talking.

"Some people ask me if I'm running away from something, but I look at it as me running to something. I think that music makes life bigger and better. What I'm doing musically now compared to when I started is more exciting and more intense, but I'm also seeing the world with a clearer perspective than I've ever done before. I feel that touring is where I'm supposed to be, so that's probably why I keep doing so many shows."

And when he's not touring, he's recording. A collaboration with guitarist Tom Freund set Harper's career in motion in 1992, but it was Fight for Your Mind, the first album with his band The Innocent Criminals, which elevated his career. Since then, there has been much to admire, be it the gorgeously emotional collaboration with gospel greats the Blind Boys of Alabama, or his current release, the intriguing, double-sided Both Sides of the Gun.

For Harper, each record receives the same love and attention.

"You mentioned the Blind Boys and, yes, it was great fun working with them. They're great and I love what they brought to me. But I didn't approach that record in any way differently than I would approach another record or one of my own records. I put the same intensity and attention to detail into every record. It's soul music, it's the roots. I just dig in and try to be as focused as I can."

One particular track off his current album has received a lot of attention. Black Rain is an edgy, charged tirade about the lack of US government sympathy for those abandoned in the wake of Hurricane Katrina. With lines such as "You left them swimming for their lives down in New Orleans" and "You don't fight for us but expect us to die for you", there's no question about where Harper stands on this issue.

"I'm really glad that people got it. It was an important song to put on the record and I hoped it would act as a voice out of America that was clear in its frustration and clear in its point as to how the majority feel about what went down in New Orleans last year."

Aside from Kanye West and his emotional outburst in the immediate aftermath, most musicians have not being so direct with their criticisms. But Harper isn't about to sling mud at his peers for their lack of opinions.

"It's a trap commenting on something like that because what I say may not read in print the same way I said it. I really am very cautious when it comes to talking about other artists and what they do or don't do.

"I will say this: I really think popular music has to get back to the true roots of American folk and blues music and what that was about. Then we'd have some real change."

Harper admits that he himself can be highly reticent when it comes to airing his own opinions. "Sometimes I'm so self-confident that it probably borders on arrogance. And then sometimes, I'm completely questioning if anything I'm saying is getting to anyone at the level I'm feeling it. Sometimes, I can't even find a comfortable medium between the self-belief and doubts, and then it's really difficult to progress."

It's probably a good time at that stage for Harper to head home and check his head at the Folk Music Centre & Museum in Claremont, California. His grandparents used to own it and the young Harper spent his youth there. ("I used to go there after school and fool around with my friends on home-made guitars.") He heard tales about this singer called Pete Seeger from his grandparents, and he'd take it all in. "That place was where music, social and cultural awareness and consciousness came together for me."

Five years ago, Harper bought the place from his grandparents. "I'm keeping it in the family. My brothers and mother still work there." It's still a museum and still provides a space for touring folk bands to ply their trade.

Most of all, though, Harper took it over to protect its past and secure its future. "I want to keep its doors open and help it to expand and thrive, but still stay true to its roots, which is Pete Seeger and If I Had a Hammer. I'm also keen to see the centre associated with the newer school, the more progressive school of folk music. I come from folk music and I want to make sure there's room for all kinds of folk music there in the future."

Both Sides of the Gun is out now on Virgin Records. Ben Harper plays Oxegen at Punchestown Racecourse, Co Kildare on Sunday, July 9th