In her quest to become the world's strangest pop star, Bjork Gudmundsdottir (yep, she has a last name) has tapped a seemingly bottomless well of weirdness.

Most are familiar with the infamous swan-dress gambit, of course, a high-fashion don't that found Bjork dressed as a fine feathered friend at the 2001 Academy Awards. But the cuddly cute singer has also gained notoriety in recent years for decking a pesky reporter at a Bangkok airport, for going AWOL from the set of Lars von Trier's "Dancer in the Dark" -- and for promptly retiring from the silver screen after dangling from a noose at the climax of that twisted film.

Bjork first gained fame outside her native Iceland with a band of spastic post-new wavers, the Sugarcubes. In the 'Cubes, the prodigiously talented (and classically trained) Bjork opted to share lead vocals with Einar Benediktsson, a boorish ranter whose main contribution involved serving as the band's onstage heckler. The group wowed crowds anyway, thanks almost entirely to the pint-size Bjork's outsize charm and to "Birthday," a shimmery slice of alt-pop canon fodder whose precocious lyrics might make even Lewis Carroll blush.

As a solo artist, Bjork has kept up the weird work, collaborating with orchestras and computer programmers, remix mavens and visual artistes. Along the way, she's issued a steady stream of sophisticated, futuristic albums, mesmerizing platters that somehow manage to be both difficult and easy listening at the same time. On the best of them, 1995's "Post," Bjork even uncorked a high-steppin' show tune -- albeit one that came outfitted with plenty of her patented shrieks, grunts, whispers and belly-growls.

With antics like that, of course, the $64,000 question quickly becomes: So what else you got? On "Medulla," Bjork's latest and most arresting album, the singer offers a look-ma-no-hands kind of answer: It's her first a cappella effort.

Or at least mostly. Sensuous set-opener "Pleasure Is All Mine" comes wrapped in a gorgeous chorus of multi-tracked Bjorks, but the track, like several others here, is also powered in part by gently throbbing percussion that sounds like a beating heart. And if you listen closely to tunes such as "Who Is It," an elastic, radio-ready pop song that could easily revive Madonna's career, and "Mouths Cradle," a purported ode to the pleasures of breast-feeding, you'll catch the occasional whoosh and squiggle of synthesizers, too.

Still, Bjork's voice is "Medulla's" lead instrument, and as ever, it's a gale force of nature. On "Sonnets/Unrealities XI," jealous words become percussive tone poetry, while "Show Me Forgiveness," appropriately enough, sounds like an invocation sung by a priest with one heavenly set of pipes.

Elsewhere, on the thumping "Where Is the Line," Bjork chips in with the catchiest whistled hook this side of Peter Gabriel's "Games Without Frontiers."

For Bjork neophytes, "Medulla" isn't the place to start. It's a beguiling disc, but austere, too -- a thing of beauty if not exactly a joy forever. Longtime fans, on the other hand, are likely to find it dazzling. "Medulla" is the least conventional album their favorite elfin woman-child has ever made. And given Bjork's track record so far, that's quite an impressive feat.

Bjork's latest, "Medulla," is a beguiling but austere CD that's best left to hard-core fans.