The story of Sweden's ABBA, whose first Washington appearance is sold-out at DAR tomorrow, is a pop fairy tale come true.

In 1966, Benny Andersson, a member of the Swedish Hep Stars, met Bjorn Ulvaeus, and they began collaborating on mostly folk material, inspired by Lennon and McCartney. In 1971, they became a singing duo called Bjorn & Benny, scoring with two minor hits, "People Need Love" and "Rock 'n' Roll Band."

Eventually their wives, Agnetha and Annifred (Anna & Frida), began appearing on the records as backup vocalists. By 1973, with "Ring, Ring" and "Waterloo" international hits, the women were singing out front, so everybody's initals were condensed into the convenient palindrome, ABBA.

Since then, ABBA'S music has covered the globe, not with clinging goo as many of their critics suggest, but with a cozy quilt of warm pop. Most of the band's million-selling earthshakers -- "SOS," "So Long," "Mamma Mia" -- can be found on the very tidy "ABBA -- Greatest Hits" (Atlantic SD 18189). Discovering their niche in rock 'n' roll history, however, is a more difficult matter.

ABBA'S sound is so extremely formulaic that the band's identify has been virtually swallowed by the awesome whale of studio production. On any sunny day, one can bop down the street and usually bump into a smiling face humming on ABBA tune. "Oh, pardon me. Are you an ABBA fan, too?" one pleasantly inquires. "Who?" is the inevitable response.

ABBA is the perfect band for the sonality as a Hanna-Barbera cartoon character; that's not only part of their appeal, but also the essential ingredient of their ploy. During ABBA'S infancy, Bjorn and Benny fell in love with the immediacy of American pop.

ABBA, is the perfect band for the '70s, because their music is nothing more, and nothing less, than an amalgamation of earlier pop styles. In particular, ABBA'S sound derives from two distinct styles of production: Phil Spector's early '60s girl group recordings (the Ronettes' "Be My Baby," the Crystals' "Da Doo Ron Ron" and Katz-Kasenetz's buble gum nuggets (1910 Fruitgum Co.'s "Simon Says" and Ohio Express' "Chewy Chewy"). Listening to ABBA's early smash, "Honey Honey," one gleefully notes that producers Bjorn & Benny have preserved the innocent connotations of the Archies' "Sugar Sugar" without sacrificing the carnal implications of Anna & Frida's siren voices.

Lately, though, ABBA has allowed a third style of pop music to infiltrate their close-knit formula -- the disco beat has been creeping into every record since "Dancing Queen." The structural question is whether ABBA can cram a third style into an economical sound that's already convoluted with pop references from another era.

"Voulez-Vous" (Atlantic SD 16000), ABBA'S sixth and latest album, is the band's first attempt to go entirely disco. Although bubble gum and disco are linked historically (Neil Bogart was directly responsible for creating both styles), ABBA seems unaware of any connection between the two, even musically. Both bubble gum and disco are manufactured forms of dance music, created as studio product, but ABBA prefers to shift from one style to the other; avoiding the necessary act of assimilation.

Consequently, "Voulez-Vous" is a wonderful mess, pure schlock of the highest order. On the title cut, ABBA sips from Chic's fountain of Kool-Aid. "I have a Dream" could be sobbing Nana Mouskouri singing along with Alvin and his giggling Chipmunks. "As Good as New" conjures up an image of the Banana Splits playing patty-cake.

Unfortunately, ABBA has grown up, and adult lust -- panting uncontrollably in disco dens -- seems to be their major preoccupation. The two naughty-naughty hits from the album, "Angeleyes" and "Does Your Mother Know," only make this fact more painfully obvious.

ABBA'S music used to be as frolicsome as skip-rope chants. One can hear this playful spirit cutting loose on their first and best album, "Waterloo" (Atlantic SD 18101). It is a work overloaded with the enchantments of childhood -- hula hoops, a candy store, King Kong, smooching during recess, every carefree delight wrapped into one fun-filled package.

"Voulez-Vous," on the other hand, is simply overloaded.