Every year for the past two decades and more, Cambridge resident and violin maker Bob Childs has organized a family reunion that is unique in a few ways - including the fact that none of the participants are technically related to him.

Childs is the guiding force and namesake for Childsplay, an ensemble of two dozen or so musicians performing fiddle music mainly from Irish, Scottish, Cape Breton, Scandinavian, French Canadian, and American folk traditions. His most distinctive contribution? He made all the fiddles and violas used in the group. Those who have taken up the bow at one time or another for Childsplay, along with Childs himself, include Laurel Martin, Hanneke Cassel, Steve Hickman, Sheila Falls Keohane, Mary Lea, Mark Simos, Lissa Schneckenburger, Sam Amidon, Joe and Graham DeZarn, and Dave Langford. Among the non-fiddling contributors have been flute, whistle and accordion player Shannon Heaton, guitarist Keith Murphy, vocalist Aoife O'Donovan, cellist Ariel Friedman, string bassist Ralph Gordon, and dancers Pierre Chartrand and Kieran Jordan.

The 2009 edition of Childsplay performed at the Cambridge River Festival and in New York City last month to mark the release of its fifth CD, "Waiting for the Dawn," and is preparing for a series of concerts this December, including at Somerville Theater (Dec. 5) and The National Heritage Museum in Lexington (Dec. 6).

As Childs sees it, his bond with this group of people is special and meaningful, and has grown deeper and richer over the years. If that's not a family, he asks, what is?

"There's a connection you feel in Childsplay that's very different from other bands," says Childs. "A lot of it, of course, has to do with the fact that the featured instruments are made by one person, and there is a consistency to their tone and timbre - a sound that is familial, although no two are absolutely, exactly alike.

"But there's more to it than that. Each instrument that I've made becomes a story in and of itself through the musician who plays it, and through Childsplay those stories are given voice together. It's such a powerful thing, and even the members of Childsplay who play other kinds of instruments are able to share in the experience."

This concept of Childsplay as a family unfolds in other ways. Within the group, over the years, have been marriages and births, as well as illnesses and losses, and voices representing a new generation are joining the ranks: When Joe DeZarn took part in the first Childsplay concert, in 1987, his son Graham - now 24, and a regular participant - was a toddler, almost the age that Childs's son Liam is now; Friedman and O'Donovan weren't in elementary school yet, and Schneckenburger and Amidon hadn't reached junior high.

Furthermore, as Childs explains, the group as a whole has grown and changed in terms of its scope and material. "It started with basically all fiddles, but we wanted to go for a more complex sound, so we began incorporating bass, guitar, banjo, piano for rhythm, and later on harp and flute, especially for slower tunes. That enabled us to put together more sophisticated and elaborate arrangements, and eventually to expand our repertoire to include songs."

"Waiting for the Dawn" is Childsplay's most extensive use of vocals to date, with seven of its 13 tracks featuring or incorporating songs led by O'Donovan, with occasional harmony supplied by Murphy, Schneckenburger and Molly Gawler. As with most other aspects of Childsplay, this development reflects an integration of musical and personal insights for Childs that reach back to a less-than-ideal childhood: Childs spent the first few years of his life in foster homes until he was adopted, and the mystery of his birth parents' identities nagged at him until well past adulthood. He often tells of a dream he had some years ago, of trying to enter a country and being led by a border guard to a room in which there was a violin, inlaid with the image of a small boy crying.

"I came to realize, eventually, that crafting violins had been a way to give voice to a part of myself for which I had no form of expression," he says. "So integrating voice with violin is part of my own maturation, as well as that of Childsplay - the revelation that there is a power in words, that one's capacity for expression can keep developing, especially when you are around people who constantly encourage and inspire you to explore the means of expression."

This emphasis on expression is certainly evident on "Waiting for the Dawn"; whatever the numbers of musicians playing at any given time - whether the full ensemble or a duo or trio - and whatever the origin or character of the tune or song in question, emotion is in more than adequate supply. Right from the get-go, in fact, as the group essays "Rattlin' Roarin' Willie," the classic tale of the musician who just can't let go of his beloved instrument (yes, it's a fiddle). Childsplay straightens out the song's familiar frenetic 9/8 rhythm into a grooving 4/4, Murphy's guitar pointing the way, and Cassel and Heaton churning out the Cape Breton "Old Time Wedding Reel" in between the verses, which O'Donovan delivers with gusto; then the group launches into "The High Drive," a joyous four-part reel by the late Scottish piper Gordon Duncan.

Two other tracks, both with Irish connections, highlight O'Donovan's presence on the CD. The first is "I'm a Youth That's Inclined to Ramble," a traditional song in the form of a dialogue between soon-to-part lovers. It's long been associated with Paul Brady, and with good reason - his memorable solo rendition gave a stark and edgy feel to the lyrical conversation, as if to accentuate the imminent sense of loss. But Childsplay takes the song to a different atmosphere, where lush, gentle strings build underneath O'Donovan's wispy, quiet voice; it's a full-bodied declaration of regret and resolve.

And then there's the medley comprising U2's "Mothers of the Disappeared" - a tribute to victims in Argentina's "dirty war" - and Cassel's original tune "The Evenstar." Cassel, in fact, did a smaller-scale, instrumental version of this set (with O'Donovan on backing vocals for "Evenstar") on her 2004 album "Some Melodious Sonnet." In this setting, Gordon's bass and Murphy's guitar provide a literal and metaphorical pulse ["Hear their heartbeat/hear their heartbeat"], and Heaton's accordion a church harmonium-like quality, while the massed fiddles collectively serve as a backing choir to a soulful O'Donovan.

"Aoife was the perfect person for this new direction," says Childs. "She is comfortable with so many kinds of music, whether it's Irish/Celtic, bluegrass, old-timey, pop and contemporary, and there's something about her voice that meshes with the violins just in the right way. So we tried to come up with arrangements that made a space for her voice, and in the mixing and mastering process the intent was to get Aoife into the center of the sound."

O'Donovan also comes to the forefront on the traditional "Sweet Sunny South," Steve Earle's "Christmas in Washington," Boston songwriter Mark Simos's "non-denominational" gospel song "Tears of Healing Rain" (aided and abetted by harmonies from Murphy and Gawler) and even "Love Me Tender," which Childs explains is a lullaby he and his wife sing to his son - here it's de-Elvised with the help of Kathleen Guilday's harp.

The instrumental-only tracks do not lack for the aforementioned expressiveness, either. They range from a pairing of Murphy's relentless 7/8 tune "SamSam Amidon" (with an equally relentless piano) and the Michael Coleman classic "Good Morning to Your Night Cap," on which Amidon and Heaton take the lead, to a medley of "Compliments to Cameron Chisholm" and the title track, written by Cassel, to the Pete Sutherland waltz "Soir Et Matin," which Childsplay dedicates to New England fiddler Kerry Elkin, who was diagnosed two years ago with multiple sclerosis (Childs says putting this track together was one of the more emotional experiences for the group).

The mix of traditions evidenced in the aforementioned sets is a big part of what makes Childsplay appealing to its participants, notes Childs. "Everybody comes from different traditions and backgrounds, so that means we all have to stretch, and people love it. The group is kind of like its own music camp: We've had Swedish players teach Scandinavian style fiddling, a classical player learn Irish bowing. Everyone wants to achieve a high level of performance, and it's great to see the commitment and desire to make it happen."

For Childs, one of the most enjoyable of the CD's instrumental sets was the trio written by Irish fiddle legend Liz Carroll: "Liam Childs/Balkin' Balkan/The E-B-E Reel." "The arrangement came together in about five minutes, just totally spontaneous and on the spot. I especially like how the ‘Balkin' Balkan' came out, where it sounds like fiddles climbing up a vine."

In fact, Childs says, putting together a Childsplay production usually requires a good dollop of time, patience, and coordination, since most of its members are full-time touring musicians. "We try to think about a year ahead. We'll find a common week or two where people can do a few concerts, and then it's a matter of generating ideas and working them out."

That's when Childsplay becomes "like a greenhouse," says Childs: "There's a very organic quality to the way the music comes together. I can say, ‘Hey, Hanneke, will you put together a set?' and they'll arrange it. But it's not just a matter of people leading arrangements; there's always an outpouring and an exchange of ideas, because after all these are

very creative people. John McGann has described Childsplay as ‘large, but very democratic.' I think that's why people have stayed so invested in it."

Perhaps it's this facet of Childsplay, more than any other, which for Childs evokes what might be called the pre-industrial dynamic of his vocation. In an era where even musical instruments are mass-produced - or else their makers are essentially anonymous - it is an increasingly rare, and wonderful, thing for a craftsman to have a relationship with those who buy his wares, especially when that rapport extends well beyond the shop.

"When I realized what it meant to me to make instruments, it drove me to create community - and a family, really," he says. "Making an instrument for someone feels like a life-time connection. The fact that I have an opportunity to broaden that connection by playing music with that person - and many others - is incredibly satisfying. I would hope that, with Childsplay, people can understand that it's possible to have that kind of special relationship."