The first time I saw Joanna Newsom, in 2004, she was standing at the edge of the Bowery Ballroom stage wearing a peasant dress, a flapper headdress, and a leather band around her arm with a feather hanging from it. She was adorable — like a child who’d picked her own mismatched outfit from a costume trunk. She was equally terrifying. When she opened her mouth, out came a bluesy caterwaul that sounded like a mute-choked horn. Nervous laughter at the sight of her quickly gave way to mesmerized silence at the sound of her.

That night Ms. Newsom was opening for Devendra Banhart, who ushered her into the inner circle of the freak-folk family. She instantly became its reigning queen and chief heartthrob. What made her so memorable — apart from her magpie fashion sense — was her whimsical audacity. She sat, Atlas-like, beneath her comically huge harp, plucking spare, enchanted tunes with nursery rhyme names like “Bridges and Balloons,” “Peach, Plum, Pear,” “Sprout and the Bean,” and “Clam, Crab, Cockle, Cowrie.”

When she played McCarren Park Pool in Williamsburg, Brooklyn, this past summer, much had changed. Her dress was more subdued, and her new material was grimly serious. As the songs stretched on and on, the requests for old favorites grew louder. People loved her for being different, but will they love her for being different from herself?

With the arrival of “Ys,” her long-anticipated second album, Ms. Newsom’s new material can be heard as it was intended, with playful string arrangements by former Beach Boys collaborator Van Dyke Parks and delicate mixing by Sonic Youth alum Jim O’Rourke. It’s a revelation: five songs, ranging from seven to 17 minutes in length, that make her past work seem like child’s play.

The comparison that jumps immediately to mind is Fiona Apple’s most recent offering, 2005’s “Extraordinary Machine.” Like that album, “Ys” is a great leap forward for the artist, and Mr. Parks’s arrangements share more than a little of the quirky genius of Jon Brion’s work on Ms. Apple’s album.

The prolixity and dreamy visuals of opener “Emily” encourages another comparison: Bob Dylan at his most baroque. Ms. Newsom wastes lovely imagery like she’s got a bottomless store of the stuff. Maybe she has: “There is rusty light on the pines tonight / some pour wine, lord, or marrow / into the bones of the birches and the spires of the churches jutting out from the shadow / and the yoke and the axe and old smokestacks and the bale and barrow / and everything’s sloped like it was dragged from a rope in the mouth of the sow below.”

That’s just 45 seconds of the song; she carries on like that for more than 12 minutes, rarely repeating a line. The closest thing to a chorus is a charming little memory jog about the difference between meteorites, meteors, and meteoroids that you don’t hear until almost four minutes in.

Mr. Parks deserves a lot of the credit for the success of the songs. At first, you don’t notice the hesitant entrance of the strings — furtive pluckings and a few ventured stabs — on “Emily.” Gaining confidence, they begin to draw tiny cursive figures behind the wordplay, giving the song a sideways energy. By the 5-minute mark, they’re battling with Ms. Newsom’s voice for the spotlight, doubling, popping, and shooting up like bottle rockets dragging little sparking tails.

The strings are even more important to the success of “Only Skin,” the 16-minute centerpiece of the album. Mr. Parks’s nimble arrangements are all that save it from becoming the opaque, plodding song that disappointed the faithful at McCarren Park. With Bjorklike natural magic, it evolves through several different musical phases. Spare swooning becomes sharp and fast oriental sounds at the 7-minute mark, setting off Ms. Newsom’s falsetto trills. Popping banjo near the end announces the entrance of the distinctive baritone of Smog’s Bill Callahan.

Though the length of “Only Skin” makes it something of an endurance test, the lyrics do reward close listening. “Scrape your knee it’s only skin / makes the sound of violins,” Ms. Newsom sings, her voice cracking with emotion, “and when I cut your hair and leave the birds all of the trimmings / I’m the happiest one among all women.” She shapes and accents the sounds less aggressively than on her first album, and strains a little less hard for the least common word. It’s further evidence that she now views herself as an artist, not a mere curiosity.

“Sawdust & Diamonds” is billed as the lone “classic” Newsom song, as it’s the only one featuring just her and the harp. It’s also the least satisfying song on the album. Despite a boiling accompaniment played with dazzling finger speed, it becomes tedious by the 10-minute mark. Ms. Newsom has not only grown beyond her old style, she’s outgrown it. The image of the pixie-ish girl with the harp no longer fits.