On her latest album, "Vespertine," Björk begins the liner notes with "I am grateful I would like to thank my son, Takk Fyoir Stutninginn," setting the stage for an album of meditation and conflict over the boundaries and terms of motherhood versus the trappings and manifestations of sexuality. The music echoes the singer's struggle in a series of dreamy lullabies, evoking both the childlike and the erotic. Björk's son is now in his teens; the album can be read as her coming to terms with him as a sexual being, and her dealing with him perceiving her as the same. While I suggest nothing incestuous, "Vespertine" is fraught with ambiguities.

Björk's approach contrasts with the relative simplicity and ease with which other pop icons have dealt with parenthood in song (Madonna's "Little Star," The Beatles' "Hey Jude"). But there is a kind of satisfaction in that Björk can't fully work through this situation, yet still treats it with gravity and thoughtfulness.

The album is more about variations than individual tracks, and taken holistically it is stronger than much of her earlier work. While there is no one standout song (cf. "Human Behavior"), the album moves with a cohesion, both musically and lyrically, that seems to follow the course of a sexual encounter, peaking at points, invested, fecund with subtext and never simple.

"Cocoon" is ripe with vaginal imagery, both maternal and sexual, including the lines "Who would have know that a boy like him after sharing my core would stay going nowhere" and later, "He slides inside ... When I wake up the second time in his arms gorgeousness: he's still inside me!!!" The line between mother and lover is blurry on "Vespertine," a theme that repeats, but never to an apparent resolution.

Later tracks continue to explore this ambiguity, most notably "Harm of Will." The most overt lullaby and also the most overtly sexual song on the album, it contains the lines "And if he has chosen the point while she is under him / Then leave her coily place crouched sucking him / For it is I / With her on knee." The song is replete with angelic vocals, a music box, a chorus and strings that follow the arc of a sexual act. The delicate climax has the overtones of religious awakening, but Björk's sensual moan must be treated as anything but completely chaste.

The final song, "Unison," is marked by Björk repeatedly singing, "I never thought I would compromise," and thankfully, she doesn't.

"Vespertine" can be read as a musical diary, less the coming to a conclusion than the documentation of a struggle. The album's strength lies in the fact that its creator seems satisfied to have no answer over an easy one.

The distinctive Björk howl is absent on this album, yet despite the subdued sound, there is a moody urgency here. Bjork's subtlety as a vocalist works in her favor; she is secure enough, and talented enough, not to wrap up her work with a bow.

In what is ultimately an intensely personal album, "Vespertine" is majestic in, and for, all of its shortcomings and unanswered questions.