JEFF HANNA is just one of the many illustrious guests on Leftover Salmon's new album, "The Nashville Sessions" (Hollywood), but he may be the best clue to the project's spirit.

Hanna, after all, is a member of the Nitty Gritty Dirt Band, an earlier hippie string band whose own Nashville sessions made history as the album "Will the Circle Be Unbroken." Like the Dirt Band before it, Leftover Salmon has also engineered a cross-generation collaboration with bluegrass and country greats.

One of those greats, Earl Scruggs, appeared on the Dirt Band's 1972 disc and its 1989 sequel and also guests on the Leftover Salmon project. Earl's son Randy, who was the producer on "Will the Circle Be Unbroken, Volume Two," is also the producer of "The Nashville Sessions," and Chuck Morris, the executive producer of "Volume Two," is now Leftover Salmon's manager.

"There are so many connections that we couldn't help but be conscious of the Dirt Band precedent," admits Leftover Salmon's singer-guitarist Vince Herman. "It was another new-grass band coming down off a Colorado mountain and visiting Nashville to play with musicians of all ages. Ours is a bit different, because we used more of our own songs instead of traditional tunes, but it's definitely in the spirit of the 'Circle' albums.

"I listened to the first 'Circle' album a lot when it first came out. Growing up in Pittsburgh, I assumed that a major role of music was to bring different generations together. That's the way it was with the polka bands there, but it sure wasn't that way with the rock bands I knew. One thing I really liked about the 'Circle' album was the way it brought together musicians of different ages and different backgrounds. Ever since I've tried to play with older guys whenever possible."

On "The Nashville Sessions," Herman and his four bandmates get to play with many of their musical heroes, not just Hanna and the Scruggses but also Del McCoury, Taj Mahal, Waylon Jennings, Jerry Douglas, Lucinda Williams and three former members of New Grass Revival--Bela Fleck, Sam Bush and John Cowan. In fact, in its mix of bluegrass instrumentation and free-form jamming, "The Nashville Sessions" often sounds like a long lost New Grass Revival album.

"There were other bands that influenced us, like Hot Rize and the Seldom Scene, but New Grass Revival was definitely at the center of our musical universe," Herman says. "You can't argue about their prowess on bluegrass instruments--no one's better than Bela and Sam on banjo and mandolin--and John has a voice to be reckoned with.

"But they also took in elements of jazz; they went looking within the songs for new ways to go. And their live show wasn't as, shall we say, stoic as the earlier bluegrass acts; Sam's stage presence made a real connection between the crowd and the musicians. In their early years, they got in a bread truck and played everywhere from little bars to big festivals. That's what we tried to do a few years later."

Leftover Salmon, which appears Saturday and Sunday at the State Theatre, got started in 1990. Herman's band, the Salmon Heads, lost some players just before a New Year's Eve gig in Colorado. He borrowed two of his friends, mandolinist Drew Emmitt and banjoist Mark Vann, from another band, the Left-Hand String Band.

Because they had little time to rehearse, they stuck to older rock 'n' roll and bluegrass songs that everyone knew. When they played the gig under the joke name of Leftover Salmon, they were surprised that the bluegrass tunes got the biggest response.

"We found that the older the tunes, the more intense the reaction," Herman recalls. "We had people slam dancing up against the walls to bluegrass songs. People weren't used to hearing that kind of thing; we were refreshing because we didn't sound like the other rock bands that were also playing the Colorado ski bars at the time. When we decided to make Leftover Salmon a real band, we figured to go with the tunes that had the most reaction.

"We had a problem, though, because the guys at the doors at these ski bars didn't know what to say when people asked what kind of music we played. So we came up with the phrase, 'Polyethnic Cajun Slamgrass.' That enabled us to include all the musical directions in our heads. Growing up in the '60s and '70s, we had so much in our heads--not just rock 'n' roll and bluegrass but also cartoon music, jazz, show tunes and so on."

Like New Grass Revival, Leftover Salmon featured banjo, mandolin, acoustic guitar and electric bass, but unlike their role models, the younger band also included a trap drum set. They found the drums were an absolute necessity in the rowdy Colorado ski bars, where dancing was the name of the game. But when Leftover Salmon finally ventured out to actual bluegrass festivals in 1994, the group was uncertain what kind of reaction the drums would get.

"It was frightening to us at first to play for bluegrass crowds," Herman says, "especially when we went to Merlefest in North Carolina in '94. Mark grew up as a bluegrass fan in Virginia, and he remembers the Osborne Brothers getting booed off the stage when they added an electric bass player. So we were nervous.

"But we had no trouble. The real traditional folks saw we were kids trying something new. Even if we weren't playing pure bluegrass, we were pointing to the masters and paying our respects. Some of that respect must have conveyed itself."

After two albums on its own label, 1992's "Bridges to Bert" and 1995's "Ask the Fish," the group signed with Hollywood Records and released 1997's "Euphoria." "The Nashville Sessions" is very different from its predecessors, however. Instead of ranging all over the stylistic map, it's unified by its emphasis on country and bluegrass flavors. And instead of sprawling at great length, the songs concentrate their improvisation into shorter, more focused arrangements.

"This is our fourth record," Herman points out, "so we're a little less worried about the album representing our live show. We were willing to go to some different places and stay there and not worry about people getting the wrong idea. Randy did a real good job of getting us to focus in and clean things up--get to the point, make a statement and get out of there.

"We liked that. On the live show, we're willing to go long, but I think records do need to get to that point. The jam-band part is the live show, where you can see people jumping around on stage and in the crowd, and you get swept up in that. On an album, jokes wear thin with repeated listenings."

LEFTOVER SALMON -- Appearing Saturday and Sunday at the State Theatre with Bad Livers.

* To hear a free Sound Bite from Leftover Salmon, call Post-Haste at 202/334-9000 and press 8121. (Prince William residents, call 690-4110.)

CAPTION: Take pieces of a couple of bands, mix, and you have Leftover Salmon.