Alasdair Roberts's music is so densely Scottish as to seem, for all its mystery and beauty, sometimes all but impenetrable, at least when the singer is engaged with his original material, as he is (mostly) on A Wonder Working Stone. (Approximately every other Roberts album, like last year's collaboration with Mairi Morrison, Urstan, is of Scottish traditional ballads.) Like Dylan -- and given the enormity of his talent it's possible to think of him as a young Scottish equivalent -- he does not create background music. He insists upon attention to the sound, the lyrics and the accompanying liner notes. Roberts' is art of an order usually called "demanding." It is, be assured, worth the effort.

The music is rooted in tradition, the lyrics influenced by poetry (ballad and formal), history and folklore, out of a specific national experience. Those familiar with Robin Williamson's post-Incredible String Band work, which brings something like actual poetry (as opposed to mere song lyrics) to folk-like Scottish melodies, will observe something of a resemblance, particularly here in "The Wheels of the World," of which one has little trouble imagining a Williamson version. Or perhaps Roberts is something of a 21st-century Robert Burns. Yet Roberts is hardly a simple imitator; actually, for that matter, successful imitation of what Williamson does, or Burns did, would be a very tall order indeed. For his part, Roberts's intelligence, knowledge and imagination are startling, and sometimes baffling, as in -- an admittedly extreme example -- this verse of "The End of Breeding."

Her carnal song unbridles vice
and brings her father to despair
With phantom limbs of fire and ice
sprawling in the sulphured air
With honey eyes and ruby lips silvered
in the moon's eclipse
What burning marl of hell is this
-- a coffin or a chrysalis

This is not, needless to say, music for the masses. Yet it is quite listenable. The often complex arrangements support sublime melodies, and Roberts is as appealing a Scottish folk vocalist as you're likely to hear these days, and that country has produced an abundance of extraordinary singers. There is also unexpected humor. "Scandal & Trance" opens with an instrumental arrangement of "Red River Valley," and at moments during its nearly eight minutes wanders into an eccentric Robertsian parody of American country music.

As is usually the case with Roberts recordings, nothing on Wonder Working Stone is short-winded. The briefest cut ("Gave the Green Blessing") weighs in at 5:36, the longest ("Wheels of the World") at 9:38. Even so, nothing measurably strains patience. Music and performance have a mesmerizing quality that, at least for me and other Roberts admirers, blurs the passing of the minutes. These are songs in which it is easy to get lost.

If you haven't heard Roberts before, though, you may want to start with the above-mentioned Urstan, a magnificent collection of interestingly arranged Scottish folk songs accessible to anyone who possesses hearing and taste. If you can get through, for instance, "The Whole House is Singing," with your eyes dry and your powers of speech intact, you have a heart, if you have one at all, of stone.