The Nitty Gritty Dirt Band isn't jumping on any bandwagon; the venerable country-rock group has always seen the value in American roots and bluegrass music.

Thirty years ago, the West Coast-based band invited a slew of country legends - Roy Acuff, Earl Scruggs, Doc Watson, Merle Travis and Mother Maybelle Carter, et al - to record traditional country numbers. The landmark three-LP project, "Will the Circle Be Unbroken," helped bridge the generation gap between so-called "longhaired" rock stars and Nashville's old-line country establishment. It went on to become the first platinum-selling bluegrass album.

Singer-guitarist Jeff Hanna says he hopes the popularity of "O Brother" isn't a passing fad.

"I'm not a musicologist or a historian," he said recently, "but I just think people like the authentic quality of music that wasn't made by machines. There's so much of that out there right now, and plenty of it's great; it's just that people want an alternative.

"The 'O Brother' phenomenon is a phenomenon onto itself. It started with the film and then spread with word of mouth on the record, without any substantial airplay, which is really great. I think it's wonderful when the music industry gets its ass kicked a little, in a positive way. The music industry tends to cruise along on a trend and ride it until it's really tired."

The Dirt Band wasn't looking to stir things up when they choose to do "Circle." In fact, it was a risky move, Hanna says. At the time, the group - featuring Hanna, John McEuen, Jimmie Fadden, Les Thompson and Jim Ibbotson - was at the height of its crossover-pop success. Its 1970 LP, "Uncle Charlie & His Dog Teddy," yielded the Top 10 hit, "Mr. Bojangles," and another pair of minor hits, "House at Pooh Corner" and "Some of Shelly's Blues."

" 'Uncle Charlie & His Dog Teddy' was the first album we were proud of the whole way through," Hanna said. "It was produced by Bill McEuen, who up to that point had just been managing us. We had a direction we were comfortable with.

"A few months after the release of that record, we were on our first major tour of the U.S. and on a swing through the South, we played Nashville, at Vanderbilt University. Earl Scruggs and his family showed up and afterward he came in and said some real complimentary stuff to John about his banjo playing. We struck up this immediate friendship. A few months later, they were playing in Colorado, where we lived at the time, and John and I went to see the Scruggs Revue play this club in Boulder and asked him if he wanted to cut a track with us. He said 'Yeah' and that started the ball rolling.

"Then we went to see Doc Watson and told him we were going to do a record with Earl Scruggs and would he like to play on it, too. At that point, Bill McEuen took the idea and really ran with it. He said 'Let's do a whole record of you guys playing with all the greats, the icons of country music.' It was stuff we cut our teeth on, even though we grew up in Southern California."

Given a budget of $22,000 by United Artists, they recorded some 30 tracks in six days in Nashville. Band members knew they were making history, Hanna says.

"There's always something you've done over the years that you wish you had done differently," Hanna said, "but that record, we're so proud of it, I'm still a huge fan of it. I listen to it today and it'll occur to me, 'Oh, that's me singing.' It's just so great to hear the magic that went on in that studio for that one week.

"It did help break down some barriers, some of them generational and some culturally. Music has a tendency to speak a language that's more easily understood than words."

The Dirt Band is still going strong today. John McEuen, who left the group 15 years ago, has rejoined, and they will be touring this summer.

"We did a handful of dates in the states last summer and then in the fall we toured Canada with Alabama," Hanna said. "This year, this'll be the first full year of touring with John back playing with us. It's so much fun; we have so much music to revisit."