Celtic music can be an arcane realm with a vocabulary of its own. Where else can a band's list of instruments alone run to more than a dozen items, distinguishing between a "tin whistle" and a "low whistle" and including a device known as a "bodhran"? (Which, incidentally, is a small framed drum that looks like a cousin of the tambourine.)

But the group known as Solas, scheduled for the 2013 Beartrap Summer Festival on August 4, has an agenda that's decidedly un-mysterious. The band's name is Gaelic for "light," and according to their mission statement the light they shed is for the benefit of audiences with preconceptions: "If you associate Irish music solely with pubs, green beer, and March, be prepared to have your mind firmly changed."

Apparently their mind-changing efforts have shown some success. No less an authority than NPR's "Thistle and Shamrock" series calls Solas "Irish-America's most influential band," and Celtic Cafe praises it as "one of the most exciting Irish traditional bands to emerge in many years."

Its core duo consists of Seamus Eagan, originally a solo artist, and Winifred Horan, formerly with the group Cherish the Ladies. The two formed a quartet with John Doyle and John Williams, and their first performance was atGeorgetownUniversityinWashington,D.C.in 1995. The following year, Solas recorded its first album and gained national visibility with an appearance on American Public Media's A Prairie Home Companion.

The ensuing decade brought a number of critically acclaimed albums--"Sunny Spells and Scattered Showers," "The Words That Remain," "The Hour Before Dawn," "The Edge of Silence," "Another Day," and "Waiting for an Echo"--and several personnel changes. Most recently,Corknative Niamh Varian-Barry replaced Mairead Phelan as lead vocalist. Along with Mick McCauley (on accordion, concertina, low whistle, and vocals) and Eamon McElholm (guitarist, keyboard, and vocals) they make up the currently touring fivesome.

Seamus Eagan has also found himself in demand as an instrumentalist for movie soundtracks. His work appears in the independent film "The Brothers McMullen" and the Oscar-winning "Dead Man Walking."

The band's promotional materials describe its repertoire as "fresh and unexpected arrangements of age-old tunes, compelling and topical originals and covers." But with a total of 10 albums under their belt, Solas decided to take on an entirely new project--an ambitious musical saga based on the experiences of Seamus Egan's immigrant great-great uncle who left County Cork for the copper mines and boxing rings of Butte, Montana, and died somewhat mysteriously at the hands of local police at the age of 25.

The first installment of the project called "Shamrock City" (a nickname for Butte, in the old days, because of its heavy Irish settlement) is a five-song EP that's currently available at gigs, and Solas has created a multimedia version of its stage show. It's also inviting fans to share their own family histories on video, at tour stops and online.