Since the ’60s, it seems that the vocal qualities of women rock and roll artists have lost their rough masculine edge, becoming progressively more feminine. The Age of Aquarius witnessed the rise of the rough growl of Janis Joplin and the melodious bellow of Nico. Joplin’s emotive roughness was followed by ’70s punk and ’80s New Wave, with increasingly-flamboyant-yet-still-masculine images of women like Souxsie and the Banshees and Talking Heads. Eighties pop bands such as the Go-Gos and Blondie first merged a characteristically feminine sound with a resolutely female perspective, epitomized by none other than the material girl herself, Madonna. The ’90s then saw the rise of solo acts like Alanis Morrisette and Tori Amos, whose whining jam ballads conveyed all the angst (and all the depth) of a teenage girl. And then come the 2000s, which have welcomed such solo performers as Joanna Newsom and Regina Spektor, women whose pre-pubescent vocal registers are more akin to a young girl than the professionally trained 20-something singers they are. On their newest record, CocoRosie adds to this growing infantile infatuation with their careful and elegant blend of electronica and opera.

“The Adventures of Ghosthorse and Stillborn” is CocoRosie’s third full-length album, and while every record has sounded unmistakably like CocoRosie — a two-girl band comprised of sisters Sierra and Bianca Casady — they each have distinct color and personality, perhaps akin to the slight-yet-significant differences in the sisters’ genetic make-up. First came the offbeat, hypnotic swirl of 2004’s “La Maison de Mon Reve,” with its odd conglomeration of sonic smatterings, which was then followed by the somber sprawl of 2005’s “Noah’s Ark.”

Their most recent album presents a new assortment of textures and patterns from the increasingly complex CocoRosie lookbook, as the girls’ juvenile vocal registers explore the cheery sounds of playground love with a hardened wisdom that’s weathered far more than high-school heartbreak. On “The Adventures,” the Casady sisters masterfully juxtapose the jagged and the lyrical, resulting in an album that combines the frivolous, the fanciful and the fine.

With the opening tracks, the girlish wail of CocoRosie can do little more than muster the simple and beautiful — if not slightly creepy — whipped confection of childhood play. Bianca takes over vocals in the beginning, lending a cautious syncopation that sounds bright and pristine. Most notable in this style is the album’s opener: “Rainbowarriors” is an M.I.A.-style jaunt on Adderall. The track has all the signature elements of the sexy Sri Lankan — chanting, convulsive outbursts and spazzed electronica — but, while M.I.A. comes off erratic (and, let’s face it, a tad bit insane), CocoRosie remains composed, even romantic.

When sister Sierra takes over, the duo takes their romanticism to the extreme, as she fortifies each of her tracks with the operatic vocal training that honed her pipes. Her songs are slower, richer and more calculated; they are lush and velvety, with her voice the creme caramel to Bianca’s sour-patched pucker. The calming “Sunshine” eloquently matches girlish pangs onto a whimsical piano progression while album closer “Miracle” is a painful meditation on a schoolyard romance: “I met a boy he wore a seatbelt/ He kissed my cheek in the back seat,” she sings.

The sweet melodies of today’s ingenues are just that, sweet. Newsom’s chirp, Spektor’s sweet soprano, even Chan Marshall’s deep plunges result in beautiful music, but there’s nothing terribly distinct about each of their sounds and perspectives. On “The Adventures of Ghosthorse and Stillborn,” CocoRosie only stokes the fire of this saccharine trend: The songs are great and the album is gorgeous, but will these artists be remembered in the years to come? It would be nice, for once, if a contemporary female singer reclaimed the individuality that characterized her powerful predecessors, instead of merely retreating into the unformed musings of girlhood.