On the occasion of its 20th year, the Irish-American folk band Solas (pronounced Suh-less) unites present and former members, among the latter such luminaries as Karan Casey, John Doyle, John Williams and Donal Clancy. Two of the founders, guitarist Seamus Egan and fiddler Winifred Horan, have never left the group. Moira Smiley, the newest addition, maintains the exquisite charms of previous Solas lead vocalists.

I've been listening to Solas since the beginning, which of course I wouldn't have done if I were not an admirer of the band. Even so, I haven't been enamored of every one of its albums, some of which seem a bit erratic and unfocused, especially when the band strays from its distinctive strengths, namely beautifully toned instrumentals and elegant singing. These sorts of qualities aren't necessarily enhanced when tied to arrangements that have sometimes felt distractingly top-heavy, particularly when electronic sounds have been brought into the mix. One understands why the band would want to experiment on occasion, but still.

Happily, the appropriately titled All These Years is a grand return to inspired acoustic form and among Solas's strongest, most consistent recordings. Clocking in at a generous 70 minutes, it offers up 16 cuts, an appealing mix of songs and instrumentals, including traditional pieces, originals and well-chosen covers. Among the last, one of two familiar to me, is Martha Scanlan's "Little Bird of Heaven," to which Solas gives a slowed-down, almost melancholic arrangement unlike any other I've heard; in fact, this feels almost like a different song.

The other, "Wandering Aengus," is the early W.B. Yeats poem -- he called it "The Song of Wandering Aengus" -- which draws its inspiration from an eerie, unsettling story in Irish legend. It's been so often set to music (by Judy Collins, Dave Van Ronk, Donovan, Karan Casey [on a solo album] and Caroline Herring, just off the top of my head) that I was a little surprised to see it here. Still, it's done splendidly, and the inclusion of Noriana Kennedy's clawhammer banjo is a nice touch, giving the treatment a hint of Appalachia. Kennedy's vocal is perfectly matched to the haunting narrative.

Another of the album's outstanding moments is a moody reading of "Willie Moore," sung by Niamh Varian Berry as if it were a tragic Irish ballad, though in fact it's a tragic Southern mountain ballad. The inimitable Karan Casey, who was Solas's original lead singer, contributes the traditional "Sixteen Come Next Sunday" (a variant of which, curiously, was in the Bob Wills repertoire) as well as Patty Griffin's Irish-flavored "Not Alone."

These plus jigs, reels and waltzes, plus other songs old and new, played and sung to the highest of standards. In other words, Solas doing what it does best when it's at its very best.