First, just to dispel any rumors or urban folklore that may be percolating: No, Hanneke Cassel has never played with U2, in concert or anywhere else.

"I wish!" laughs Cassel, a native Oregonian who has been living in Boston for the past several years - that is, when she's not bringing her special brand of Scottish fiddle music to almost all corners of the earth.

But Cassel has included U2 in her repertoire, notably an instrumental version of their song "Mothers of the Disappeared" on her 2004 album "Some Melodious Sonnet" (she reprised the arrangement - this time with all lyrics - for her appearance with the fiddle ensemble Childsplay; you can hear it on their recent album, "Waiting for the Dawn"), and makes no secret of her admiration for the Irish rock band.

"I love Bono," says Cassel, who regards him as "one of the best performers," along with Scottish fiddler Alasdair Fraser, a major influence on Cassel. "He has a lot of charisma, and he brings sincerity to what he does. I like performers who believe in what they're doing.

"I just like the fact that the band's been together all this time, they've grown to be technically proficient, but they don't forget about the soul of music."

Neither does Cassel. The passion and emotion she brings to her playing, along with her uniquely American interpretation of Scottish fiddle tradition, have helped make her one of the most popular Celtic music performers in the US today - and her recently released CD, "For Reasons Unseen," will undoubtedly give her reputation a further boost.

"Hanneke Cassel is brilliantly talented young performer who deftly walks the line between trad and avant garde," says Earl Britt, who maintains the New Celtic Revival blog and podcast. "She's intelligent, gifted, and worthy of mention in a class with the likes of Liz Carroll or Eileen Ivers."

For all her accomplishments as a performer, Cassel has cultivated another important identity: as a teacher and mentor to young fiddlers in New England and elsewhere. And in recent years, Cassel has found another dimension for her music, and for her faith, in visits with disadvantaged children in China and, last month, in Kenya.

So it's a little surprising to find that, initially, Cassel wasn't sure she liked Celtic music -- and once she did, thought that Irish, not Scottish, music would be her stock in trade.

"When I was 17, I went to the Valley of the Moon fiddle camp in California," recalls Cassel. "I saw Athena Tergis there, and I just got totally into Irish music; I was in awe of her. She taught me my first Irish tunes. Then I met Liz Carroll at Mark O'Connor's music camp, and she made a big impression on me, as you can imagine. So, Irish music was really the biggest part of my life at that time.

"And, hey, I still love Irish music," says Cassel, who has performed with Cherish the Ladies and the Cathie Ryan Band.

But all those visits to Valley of the Moon and other fiddle camps, and her tutelage under Fraser, among others, wound up pointing Cassel more and more in the direction of Scottish music: In 1997, she won the US National Scottish Fiddle Championship (she won the junior championship in 1992 and 1994). Yet while she continued to explore the Scottish tradition, Cassel began to write her own compositions and developed a different sound. The Scottish style - which she defines as having an "up-and-down, vertical quality" with percussive, flamboyant grace notes - is apparent in her playing, but there are characteristics that hint at something else, whether it's an alteration in bowing rhythm, for instance, or an improvisational run in the midst of a medley.

"I call it the ‘American style' of Scottish music," says Cassel. "It's not Appalachian, it's not Texan, but it's definitely American."

"For Reasons Unseen" is her first release since 2006 in this Scottish-American hybrid genre (she did a seven-track CD in 2007, "Calm the Raging Sea," featuring instrumental and vocal interpretations of hymns), and like most Cassel albums, it is a kind of musical travelogue for the past few years - many of the tunes commemorate a journey or adventure, an event in the life of a friend or family member, or simply an in-joke or turn of phrase that caught the ear of Cassel and appealed to her considerable sense of whimsy and fun.

Cassel's albums also tend to involve numerous guest musicians, whether it's her regular support band members Keith Murphy (guitar), Christopher Lewis (guitar) and Ariel Friedman (cello), or more far-flung friends she has accumulated over the years, including Fraser, Natalie Haas (cello), Brittany Haas (fiddle, violin), Rushad Eggleston (cello), Casey Driessen (five-string fiddle), and Ryan McKasson (viola), as well as Lissa Schneckenburger (fiddle) and Laura Cortese (vocals), who along with Cassel are part of the all-too-occasional fiddle band Halali.

The opening track, "Ides of March," written for her mother, showcases the refined yet expressive aspect of Cassel's work, her soulful fiddle riding atop Natalie Haas' gentle cello and Cassel's persistent but tender piano, Schneckenburger adding an equally plaintive second voice later on in the track. "Scandalous" - with a veritable string section supplied by Friedman, Eggleston, Kimber Ludiker and Kellen Zakula - and "The Crane Estate" are similarly stately and elegant yet impassioned.

As anyone who's seen Cassel perform live or - better yet - call a ceilidh dance knows, she has equal affinity for the more rugged, hard-charging facet of Scottish music, and demonstrates this aptly on a medley of traditional strathspeys and reels; Driessen and Eggleston join her for this, sounding at times like a delightfully deranged string quartet ("Oh yes, we had a lot of fun with that one," she says).

But two tracks, "Jungle Java" - featuring a sort of Celtic scat vocal part for Cortese and Hannah Read - and "For Reasons Unseen/Rong Hua (Velvet Flower)," reflect one of Cassel's more compelling experiences of the past several years, her visits, and deepening connection, to China. In addition to giving concerts, meeting Chinese musicians and even running occasional ceilidhs ("I've actually taught ‘The Virginia Reel' in Chinese. It's getting to be like ‘The Shanghai Urban Ceilidh.'"), she has visited orphanages and spent time with the children there: "Jungle Java," she explains, is the name of a café that doubles as a home for street children.

"It was incredible to listen to the stories there: One of the girls had been kidnapped from her family at age 5, and had entered the home at age 13. I decided right then and there that I had to make this CD, and that I would write something about this place."

If "Jungle Java" represents the inspiration for the album, she adds, the "For Reasons Unseen" track is meant as its mission statement. "I've always liked that title - it was actually the name of a band some friends of mine were in many years ago - and when I had the experience in Jungle Java, it seemed to take on a whole new meaning: about not knowing why something happens, but that it turns into something wonderful."

In that context, the Chinese song "Rong Hua (Velvet Flower)" - a lament about a girl in war-time and the hardships she undergoes - which is paired with "For Reasons Unseen" functions as a coda of sorts. "This song just made me think about the commonality in folk music. No matter what part of the world, folk music all seems to come from the same place, a place of sadness and humor, and people express it in ways that are far more similar than we might think."

For Cassel, her travels to China have helped to reaffirm her religious faith, which she has neither particularly downplayed nor promoted in her musical career. "I've never made a conscious effort to broadcast it, it's been there all along. There was a concern I had, I suppose, about not wanting to be grouped in with ‘Christian music' at first. But I do think that, as you get older, you become more confident about who you are. I like Scottish music and I'm a Christian, but people know who I am, so there's no labels to worry about.

"The things I've seen in China, and elsewhere, make it so apparent to me where God is, and I have a lot of joy because of that."

Another source of introspection for Cassel is seeing some of her first Boston-area fiddle students come of age as musicians with their own identities, such as Katie McNally - who had her first headline show at Club Passim recently, which Cassel attended - Amanda Cavanaugh (who released her first CD last year and was in Childsplay along with McNally last fall), and Abbie MacQuarrie, who is completing her undergraduate degree in Scotland.

"When I moved here to attend Berklee, I started teaching some local kids, and over the course of time there were several girls I saw regularly, and we just developed a very close bond," she says. "I was fortunate enough to have a wonderful fiddle teacher in Carol Ann Wheeler in my early teens. I think because I remembered how hard life can be at age 13, and how nice it was to have an older woman to look up to, I wanted to do something similar for these girls.

"I'm very proud of them: They work very hard at the music, and I know they'll do very well."

Cassel will be performing with Highland Dance Boston on May 23 at the Boston University Dance Theater. The concert will feature choreographed dances set to music from "For Reasons Unseen" and some of Cassel's previous recordings. For ticket information and other details, see highlanddanceboston.org/hdbconcert.html.