The Thorns are a supergroup with a difference. The trio's hallmark is three-part vocal harmonies, the kind that haven't been widely popular since the '60s heyday of the Byrds, the Beach Boys and Crosby, Stills & Nash.

But the three talented singing/songwriting Thorns -- Matthew Sweet, Pete Droge and Shawn Mullins -- don't care that their sound goes against the current grain of pop music.

They're all seasoned performers with smallish but loyal followings, and they were content to make their self-titled album just for the pleasure of it. The fact that their side project has sold more than 100,000 copies and taken them on tour with the Dixie Chicks and John Mayer is just icing on the cake.

"We had no idea that the songs might be commercial," says Mullins. "It's a bit of a throwback -- the way our harmonies are laid out, the fact that there are no electronic drum loops. We're bringing back music that really hasn't been heard in a while."

Mullins says the group began as a casual get-together that unexpectedly took off.

"It started as more of a writing project than a band," he recalls. "Pete and I had written a couple of songs together. But when Matthew came in, we found that our voices were blending really well and the direction seemed natural right away. It was pretty neat."

The three spent two weeks writing and singing at a ranch in California's Santa Ynez Valley.

"The idea was for it to be truly collaborative," says Droge. "Not to bring in complete songs, but rather ideas to work on together. We were trying to create a sound and a style for the band, rather than making decisions the way we would in our solo projects.

"The songs were really custom-tailored for our harmony vocals. Our sights were set on this three-part harmony thing, and it all followed that intention."

Of course, it wasn't necessarily easy for three people who were accustomed to having control over their music submit to each other and producer Brendan O'Brien, but they sensed the results would be worth it. And they were right: The lush, effortless-sounding harmonies on songs like No Blue Sky, I Can't Remember and Runaway Feeling are testament to the success of their mission.

"The hard part was letting go in the studio," Sweet recalls. "But it was a good experience for me. I've never really done anything with other people, so just having that boot camp was good. And now my voice sounds a little bare by itself. It's kinda weird -- it doesn't feel like enough."

"Yeah, I've been doubling all my vocals ever since," admits Droge.

The Thorns bring their sweet harmonies to Lee's Palace tonight.