Tim O'Brien is one of the most talented -- and perceptive -- performers in acoustic music today. He realizes that it takes more than just a random collection of songs to make up an album and, as a result, consistently produces CDs that are on a plateau above those of most of his contemporaries.

Naturally, he runs the risk that some people won't like the particular theme he chooses for an album, be it his Bob Dylan covers of several years ago, or the Celtic/Appalachian thread he follows in The Crossing. Fortunately, commercial acceptance isn't his primary consideration, as he recently made known in Bluegrass Unlimited. He's all the better artist for it, and his fans are all the happier.

O'Brien has been a musical explorer ever since his bluegrass days with Hot Rize, and with this CD, he examines the way that Celtic music influenced the music of the Scots-Irish settlers who settled in the Appalachians. He returns to Ireland and its music to look for his roots, or "tubers," as he says in "Talkin' Cavan," a hilarious talking blues based on his journey back to the old homestead. There's a wide variety of music on this CD, and a wonderful assembly of guests.

One of these, bassist supreme Edgar Meyer, provides an eerie introduction to the first cut, "Ireland's Green Shore," a traditional "dream" song O'Brien derived from the Hammons Family. Also present is Stuart Duncan's haunting fiddle, and Del McCoury, a real high and lonesome voice of the mountains. McCoury's harmony is set way back in the mix so that it becomes ghost-like. It's a judicious choice, since it can be quite overpowering, being the finest (and strongest) single voice in bluegrass today. Pierce Pettis is present as a co-songwriter on "A Mountaineer is Always Free," and his musical signature is clear in the song's slightly rocking rhythms and melody. Seamus Egan's low whistles and Frankie Gavin's fiddle work together seamlessly to provide the true Celtic voice.

The title track which follows is a rollicking instrumental in which O'Brien shows his fiddle expertise. (Is there anything he can't play well?) The music is further driven by Ronan Browne's uilleann pipes and Egan's bodhran. Danny O'Keefe's "Into the West" has a Celtic feel, but the verse and the bridge are musically unpredictable, making for a more contemporary change of pace. John Mock's low whistle is particularly effective. "Wagoner's Lad," a song associated with Buell Kazee, returns us to tradition, with a lovely duet between O'Brien and Kathy Mattea. It's also graced with fine ensemble work from Dermot Byrne's accordion and Mairead Ni Mhaonaigh's fiddle. The duets continue with "Down in the Willow Garden," pairing O'Brien with Paul Brady in the kind of precise harmony singing that Jimmy Martin and Bill Monroe used to provide -- every scoop and turn and bent note is in perfect alignment. Wingtips are touching on this one.

It's mando-giant time next, with Darol Anger and Mike Marshall joining O'Brien in a slip jig, "The Kid on the Mountain." The playing is fresh and perfect, as expected. It's an instrumental wonder, and it's nice to hear Anger and Marshall slip back into more traditional garb after their recent adventurous and mind-bending Jam collaboration.

The album's sole disappointment for me is "Lost Little Children," an O'Brien/Robin and Linda Williams song. Depicting the plight of Irish children waiting for their parents to claim them in America, the song seems overly obvious and too sentimental, though it's nice to hear Tim and his sister Mollie singing together again. The spirit soars once more with an instrumental of "Ireland's Green Shore," with Dirk Powell making a clawhammer banjo appearance. Unlike the first version, this one has a pure Appalachian voice all the way.

Two ballads follow, both titled after men. The first, "John Riley," is a tonally and emotionally minor key song about an Irishman who roams from Ireland to Canada to America to Mexico, changing allegiances as he goes, and the second is about a Pittsburgh native named "Rod McNeil," who O'Brien affectionately remembers as a kind and generous man who booked bluegrass performers into his Moose Lodge. It's an odd subject for a song, but is profoundly moving, a fine memorial for a fine man.

A little Earl Scruggs is better than none at all, and the banjo god appears here with O'Brien and fiddler Gavin in a medley of "Lord McDonald" and "Cumberland Gap," another rousing blend of Ireland and Appalachia. After the aforementioned "Talkin' Cavan," which reminds us of what a great guitarist O'Brien is, we have "The Ribbon in Your Hair," a ballad that sounds more like Nashville than Ireland, with the sweet-voiced Maura O'Connell on hand. We get another Irish/Mountain medley with "Yew Piney Mountain/Dusty Miller," and the album concludes with "Wandering," a perfect closer. It's specifically about Irish "gypsies," but reminds us that all this music was created by people wandering from their homes, first to the shores of America, and then into the Appalachians.

It also makes us aware that the title of The Crossing refers not only to a crossing of roads, but a crossing of two cultures that produced a distinctive and emotional music bearing traces of the old Celtic sounds, yet having its own distinctive and American voice. O'Brien and his musical guests skillfully make both styles of music their own, and give us an album laden with deep feeling, great joy, and ancient tones, a true Celtic/American treasure.