Few bands go looking for the metaphorical crossroads, but once they encounter it, there’s no turning back. So was the case last year with Annalivia, the Greater Boston-based group that since its beginnings five years ago has drawn plaudits for its intelligent union of Irish and other Celtic and British Isles traditions with American roots music, plus a gradual incorporation of original material.

The band underwent a membership change, as fiddler Brendan Carey Block and string bassist/banjo player Stu Kenney departed, and fiddler-vocalist Mariel Vandersteel, with solid foundations in Celtic and old-timey/Appalachian as well as Scandinavian music, joined co-founders Flynn Cohen and his wife Liz Simmons, and fiddler-vocalist Emerald Rae. With a string of performances this year that includes New Bedford Summerfest, BCMFest, One Longfellow Square in Portland, Me., The Basement in Northampton, and the New Haven International Festival of Arts and Ideas, and now, their brand new CD (and third overall), “The Same Way Down,” Annalivia has moved well along from the crossroads of 2011.

Annalivia will formally mark the release of “The Same Way Down” with a Sept. 6 concert in Harvard Square’s Club Passim, with guitarist-singer-songwriter Jake Armerding (who produced the CD) as the opening act.

Keeping with its new direction, Annalivia has officially junked its previous self-described “alt-trad” label in favor of an appellation Cohen and Simmons say is truer to the band’s character: Celtic-Americana.

“The vision for Annalivia has always been broader than one genre of music,” says Cohen, who plays guitar and mandolin and shares lead vocals with Simmons. “We were going for a more rounded American folk sound but without changing the influences that have always been important to us, and ‘Celtic-Americana’ reflects that. For me, it’s not only been bluegrass and Appalachian, but Irish-style rhythm guitar; for Liz, it’s Irish traditional singing along with Irish and other folk guitar styles; for Emerald, it’s Cape Breton, Scottish and Irish fiddle, and now more old-timey.

“With Mariel, who plays a lot of old-timey but has experience in other traditions, we have a sound that we can bring to a wider audience but not be marked with a particular cultural/ethnic stamp.”

Says Simmons, “What we’ve done is bring the sound of Annalivia home to our roots. It’s not like we wanted to leave behind the flavor that we’d had. As we thought more and more about what was at the core of Annalivia, we knew how much we loved digging up Appalachian ballads -- and, of course, most Appalachian ballads have their ancestors in the English, Scottish, and Irish traditions.

“So even though there are some aspects of the band that are different now, there is still and always the desire to explore those connections between American music and its forebears. That’s why the new album sits alongside the previous two very well.”

It’s common practice for bands to recruit someone whose acquaintance they’ve made through jam sessions or occasional gig opportunities, but Cohen, Simmons, and Rae had had little previous musical experiences with Vandersteel. Still, in a folk/acoustic scene like Boston’s where degrees of separation are typically measured by far less than six, the Annalivians were certainly familiar with Vandersteel’s body of work. A Berklee College of Music grad (like Rae), she’s best known as a member of Blue Moose and the Unbuttoned Zippers -- a quartet known for its creative, inimitable mix of Appalachian/old-timey, Scandinavian, and their own compositions -- and in more recent years has performed with Laura Cortese’s Acoustic Project, which fuses traditional and indie-pop sounds in a string quartet-type setting. Last year, she released her debut solo album, “Hickory.”

But California native Vandersteel is very much at home in the Celtic realm, and she traces her interest all the way back to her early childhood, when she saw master fiddler Seamus Connolly perform in Concord, Mass., where she and her family were living at the time. While her initial training was Suzuki and classical violin, Vandersteel could never quite get the fiddle out of her mind. By middle school, she says, she felt less and less connected to the music she was playing, to the point where she broke down in tears during a lesson. Then she went to see a concert given by Scottish fiddler Alasdair Fraser and his students, and was struck by the energy and unmitigated joy in the music. She immersed herself in Celtic traditions and set off in a new direction, one that eventually led her to Boston, Berklee, Blue Moose, and now, Annalivia.

“We wanted someone who was experienced in old-timey fiddling,” says Cohen. “There are some fiddlers who are really great at it, but not necessarily for concert-type settings. Mariel is very used to performing, and as an added benefit, she has the chops for playing all kinds of styles that fit in with the sound we have.”

“The funny thing is,” recalls Simmons, “Flynn, Emerald, and I all thought of Mariel independently of one another. Flynn said, ‘What about Mariel?’ and I said ‘That’s what I was going to say,’ and then when I talked with Emerald, she said, ‘Why don’t we ask Mariel?’”

“I was definitely excited to get Liz’s call,” says Vandersteel. “Individually, I always liked their playing and singing, and I loved how they brought it all together in Annalivia. I hadn’t played much Irish music in a while, so that also was appealing – and at the same time, they wanted to branch out more into the American roots side of their music.”

Vandersteel’s settling-in period was a fast-paced affair, since the band had decided to make an album that would capture the new Annalivia sound, with plans to go into the recording studio in April of this year. But first, they had to launch a campaign via Kickstarter, the website-based funding platform, to help support the CD project. And, oh yes, they had to put together the new material so they would actually have something to record.

“It was a big effort, but having that very intensive goal right off the bat was good for us,” says Vandersteel. “Coming up with ideas and working on them in a concentrated period of time -- it became a glue that drew us closer together.”

To round out the CD, the band brought in a couple of key guest musicians: Corey DiMario, former string bassist with the band Crooked Still, and Berklee student Lukas Pool, a five-string banjo player (vocalist Aoife O’Donovan, DiMario’s Crooked Still colleague, also appears on one track).

“We wanted bass and banjo, because that’s always been part of Annalivia,” explains Cohen, who managed to record his third solo album, “Fierce Modal,” even as Annalivia prepared to hit the studio. “Stu is a fantastic musician I’ve always enjoyed working with, and he developed a lot of his style through playing for contra dances. Corey comes at it from another perspective: His rhythm is informed by his background in jazz as well as Celtic and other folk music. Lukas, with the five-string banjo, is obviously steeped in Americana, but he’s also had the experience of playing with Celtic-influenced musicians. So, again, we felt we could take some familiar elements of Annalivia and present them in a new way.”

Fully appreciating the new Annalivia requires listening to “The Same Way Down” with a minimum of distractions at least once or twice, because there are subtleties within subtleties. The CD’s first track, “False Sir John,” is a perfect illustration of the band’s modus operandi. It’s a ballad with origins stretching back centuries, a particularly compelling take on the theme of the lover who turns out to be a cold-blooded killer bent on robbing the unsuspecting and seemingly helpless lady-in-distress. Simmons heard this version through a recording of legendary American folksinger Jean Ritchie, but she began playing around with the melody, turning it from a major to minor key with a jazzy texture.

Rae and Vandersteel provide a suitably dramatic backdrop with a series of plucked notes for the first few verses and again at the very end; for the verse in which Sir John’s true nature is revealed, they switch to bowing their fiddles, underscoring the plot twist. Cohen’s mandolin appears about a quarter of the way through, his chording lending some graceful color, and gradually rising to the top of the mix for a solo that leads to the song’s epilogue. Simmons, for her part, doesn’t push at the lyrics but lets the narrative speak for itself, tweaking the melody in a few spots to great effect.

“I think we’ve become very confident in our skills as arrangers,” says Simmons. “’False Sir John’ evolved in a very organic way: Once I came up with the new melody, we started thinking about a rhythmical thing to go with it, and Emerald got the idea for this plucked riff on fiddles, and the song just took off into a new realm.”

The tune set “New Mown Meadow” offers perhaps the best glimpse of the band’s influences in one kaleidoscopic fell swoop. It starts with Rae’s tender “So Long Old Friend,” the harmonized fiddles sounding Scottish and American at the same time, until Cohen’s flat-picked guitar and Pool’s banjo lead the segue into Cohen’s composition “The Fine Apron,” which ably straddles the Irish/Appalachian fence, and then the band -- with particularly strong contributions from Pool and DiMario -- rides on Rae and Vandersteel into “New Mown Meadow,” a traditional Irish reel (Cohen learned it from Boston fiddler Brendan Bulger) in a very distinctive dorian mode.

“That set is where the ‘Celtic-Americana’ persona of Annalivia really shows,” says Cohen. “You have two contemporary tunes that are American-sounding but go beyond old-timey, and then a classic Irish reel that came to us from a Boston musician with Irish-American heritage.”

Another Cohen original, “Snag,” meanwhile, is an example of what happens when musicians who are adept in both theory and application take on a challenge. Vandersteel and Rae’s loping fiddles begin “Snag,” Cohen’s mandolin, Simmons’ guitar and DiMario’s bass settling in by turns on what appears to be a traditional tune’s conventional A part/B part structure. The momentum builds until, suddenly, the fiddles back off into playing rhythm with Cohen and Simmons through a series of exotic chord changes, before the tune resumes its previous form.

Here’s Cohen’s explanation of the tune: “’Snag’ was an experiment in modulation I had in my notebook for a few years. It’s based on the Joni Mitchell song ‘Free Man in Paris,’ which to me is an example of how pop music inspired by jazz rubbed off on ‘70s songwriters. I wanted to write a fiddle tune over these chord progressions -- which you never hear in Irish music -- and I worked it out on tenor banjo. But it was hard to harmonize all the quirks in the tune, and I wondered, ‘What are we going to do?’ So Mariel and I worked together one afternoon, and I wound up writing a bridge that sealed the deal.”

Vandersteel laughs, “I’m all for quirkiness. Arranging that piece was a lot of fun -- it’s different, but it still works.”

Yet Annalivia knows there’s definitely something to be said for simplicity, especially where traditional music is concerned. The album’s concluding track, “Turtle Dove” (also known as “10,000 Miles”), is grounded by Cohen and Simmons’ achingly winsome vocal duet, and backed by nothing else but twin fiddles, kept at a respectful distance, and the drone of a sruti box -- a kind of compact-sized pump organ. The song has its antecedents throughout British Isles folk tradition, but this version is patently American, and so is the band’s arrangement: It has the feel of sitting in a lonely little church somewhere in the mountains of Tennessee.

Steeped in ballad/folk traditions though they may be, Annalivia has increasingly turned to its own songs, especially Simmons, who authored or co-authored three of the CD’s tracks. Two are what Simmons describes as “somewhat autobiographical”: “Restless for a While” (written with Boston-area musician and songwriter Mark Simos) is about the struggle to settle down, even with the promise of apparent happiness, while regret and acceptance are at the emotional core of “Wherever We’re Bound” (written with Simmons’ longtime friend Sarah Yanni). “Deepest Water” muses on love as a form of drowning, a metaphor not far removed from folk tradition, which is what Simmons had in mind.

“When I’ve written songs, I’ve tended to be more observant of the world around me,” she says. “With ‘Deepest Water,’ I wanted to write something that could fit comfortably with the traditional songs we do. So I pulled a few lines or phrases here and there, to suggest a connection to the tradition and its universal themes in human experience.

“If you listen to American music, you hear the mix of Celtic and African, and other influences, and I think Annalivia is all about that ‘melting pot.’ There is always something to add.”

For tickets and other information about Annalivia’s CD release concert at Club Passim on Sept. 6, go to passim.org.