These guys just don't rest.

The Chieftains, who kept traditional Irish music alive almost singlehandedly for decades before its current renaissance, keep churning out high-quality albums. But, while some long-standing artists are content to keep producing more and more of the same ol' sound, the Chieftains keep breaking new ground that opens their music up to new audiences while introducing new and established artists from other field to the Irish milieu.

The band's latest, Tears of Stone, maintains the trend. This time, the Chieftains share their spotlight with an outstanding assortment of contemporary female artists, many of whom were previously strangers to this brand of music. Some, like Sinead O'Connor, Loreena McKennitt, The Corrs and The Rankins, have gone the traditional route before. But who'd have expected to hear the likes of Bonnie Raitt, Natalie Merchant, Joni Mitchell and Joan Osborne on an Irish album?

In some cases, however, this merger has resulted in making the Chieftains sound more American than it has in making the American folkies sound Irish.

Take Bonnie Raitt's "A Stor Mo Chroi," for instance. Even though Raitt mastered four words in Gaelic to sing this mournful ballad, there would be no mistaking her for an Irish balladeer despite Derek Bell's delicate harping. Ditto for Joni Mitchell, whose somber "The Magdalene Laundries" is one of the few nontraditional songs on the album.

Former Maniac Natalie Merchant sings brilliantly on "The Lowlands of Holland." While she still sounds completely non-Irish, her voice blends neatly with the band's subtle Irish backdrop. Joan Osborne resurrects "Raglan Road," a song overdone in too many Irish-American pubs, but I found myself enjoying her distinctive singing style on this one anyway. The same can be said of singer Sissel's delicate presentation of "Siuil a Run," which has become a popular tune since its inclusion on The Lord of the Dance performances.

Mary Chapin Carpenter can't lose her American accent, but kudos for learning the lyrics to "Deserted Soldier" in Gaelic. The addition of the lilting "Kerry Slide," featuring a handful of Chieftains and Matt Rollings on piano, is a high point on the album just because there is so little of the band's usual all-instrumental flair.

The inclusion of "Sake in the Jar," a Japanese rendition of the old saw "Whiskey in the Jar" composed by Akiko Yano and Paddy Moloney, was inspired. Yano sings the tune in perfect counterpoint to the Chieftains' Irish/Oriental accompaniment.

Another standout is "Danny Boy." Yes, believe it or not, I just wrote praise for the tune which is, more than any other, the bane of musicians struggling to play real Irish music in America. But this lean, stripped-down version sung by Diana Krall is worth hearing, and Paddy Moloney's uilleann pipes add a special air that carries the right touchof melancholy without being mawkish.

Sinead O'Connor has really been making a place for herself doing traditional collaborations in recent years, and she reunites with the Chieftains here to sing the melancholy "Factory Girl." One of these days, I hope O'Connor does an entire traditional album, including some faster-paced stuff like her version of "I am Stretched On Your Grave" (which is actually based on an Irish traditional song, "The Unquiet Grave") from her shock-rock days.

"Ye Rambling Boys of Pleasure" brings Canadian singer Loreena McKennitt back to the Celtic roots which helped launch her career. It's a good track featuring McKennitt's harping abilities as well as her usual strong vocals, however, except for one brief interlude, it sounds like the Chieftains sat this one out.

Anuna reprises its Irish choral sound with the Chieftains and Brenda Fricker for "Never Give All the Hear," based on a poem by William Yeats. And the Chieftains join with Nova Scotia's Rankin family for a lovely choral rendition of "Jimmy Mo Mhile Stor."

The biggest flaw I found in the album is its focus on ploddingly slow ballads, ignoring the more energetic tunes which better highlight the Chieftains' strengths. This isn't a collection to get the foot tapping or the heart pounding quickly.

One of the liveliest songs, and one of my favorites, on this album is "I Know My Love" featuring Irish pop band The Corrs. Also outstanding is Tears of Stone's only instrumental piece, "The Fiddling Ladies," featuring fiddlers Eileen Ivers, Natalie MacMaster, Maire Breatnach and Annbjorg Lien. Finally, the band has come to life!

Generally, I like my Chieftains a little more animated than this. Although there are some real gems on Tears of Stone, this isn't one I expect to listen to as repeatedly as I have some of their earlier releases. In fact, I think this has put me in the mood for their previous collaborative effort, Fire in the Kitchen.