Björk and Lars von Trier didn't really see eye to blind eye when he directed her in ''Dancer in the Dark'' a few years back, but the mercurial singer might have absorbed more of the contrary filmmaker's ethos than she realized. With his Dogma 95 ''Vow of Chastity,'' von Trier dismissed supposed artificialities like sets, props, and scoring. In the similarly austere yet extravagant Medúlla, Björk ditches bourgeois frills like strings and drum machines in favor of, exclusively, the human voice. Well, near exclusively; perhaps still wary of complete dogmatism, she allows cameos on a few tracks by the odd bass synthesizer, piano, or (now she's getting carried away!) gong. But aside from those passing instrumental cheats, Björk is taking a big, fat Gregorian chance on full-on a cappella.
Historians among us might wonder if there's a good reason no major rock figure has attempted an all-vocal album since Todd Rundgren's A Cappella in 1985, a moderately amusing if literally long-winded experiment in vocally mimicking real instruments. There's a little of that sort of ear trickery in Medúlla; five numbers utilize Rahzel, formerly of the Roots, as a human beat box, and one has frequent Philip Glass vocalist Gregory Purnhagen credited as a ''human trombone.'' But mostly, these voices are meant to sound like voices, whether Björk is wailing against the Icelandic Choir's wall of sound or madly multitracking herself like The Matrix's Agent Smith. Besides all these mass exhalations, there's a lot of flesh, bone, and blood in the lyrics, too (''Smooth soft red velvety lungs are pushing a network of oxygen joyfully through a nose...''). She's like a convert to nudism, suddenly convinced that ''gear'' is the equivalent of a heavy coat in May. Beware: Her evangelistic zeal is so strong, she'll soon have you shunning electronica and skipping absentmindedly through the park in your birthday suit too.
Björk began recording the album with those darned old instruments before her au naturel epiphany, but only a couple of tracks belie their origins as conventional pop songs. Most easily digestible is the peppy, nearly hip-hop-flavored ''Triumph of a Heart'' tucked away at disc's end, as if a reward for making it through the more challenging passages. Leading up to that, you get a few sinister-sounding examinations of human behavior whose growling, gulping, or moaning will alienate some ears. ''Submarine'' has guest Robert Wyatt warbling for help in queasy falsetto, sounding like Carl Wilson trapped under ice. Her strikingly beautiful Olympics song, ''Oceania,'' is more rapturously aquatic, the computer-enhanced choir behind Björk suggesting a cosmic harem of pleased dolphins. Here she imagines herself as the sea itself, proud of all the belegged creatures she's spit out onto land over the last hundred million years. It's the nearest evolutionists have come to having their own gospel tune.
Björk has said a guiding rule for the album was ''not to sound like the Manhattan Transfer or Bobby McFerrin.'' Well, duh -- but if that was hardly a danger, there was every likelihood that the album's synths-for-larynxes quid pro quo would be remembered as a stunt, at best, instead of one of her best efforts. To anyone approaching Medúlla with that apprehension, we offer these four words: Don't worry, be happy.