The new Steely Dan record comes out today.

Not a sentence you get to use that often. Twenty years have come and gone since Walter Becker and Donald Fagen -- who lorded over the 1970s with a string of hits from "Do It Again" and "Rikki Don't Lose That Number" to "Peg" and "Babylon Sisters" -- last released an album of new songs. They worked solo for years before regrouping in the mid-1990s for several tours, a witty Web site and a live album.

Now comes the new record. And one old question.

First things first. "Two Against Nature" is a triumph and then some, as effortless, joyful and sly as anything from the duo's heyday. Funky hooks, milky harmonies and tight horns blend in a smooth backdrop to Mr. Fagen's sardonic vocals, which range over subjects including bad love, good love and personal apocalypse.

In other words, it's a Steely Dan record. "Two Against Nature" could have been recorded in 1979. It also makes perfect sense in 2000.

And that's the question. Lots of bands have been doing it the same way since the 1970s. Lots of others have altered their sound to stay current. But only a handful have stuck to their guns and sound vital today. Why does the Becker and Fagen formula work while others flop?

For a measure more objective than my ears, consider: Both of Mr. Fagen's solo efforts received Album of the Year nominations, most recently in 1994. And the band has kept a loyal following despite not touring for most of its salad days and not existing for even longer. Hundreds of fans have filled the Steely Dan e-mail bag; several have started Web sites; and countless others keep the albums in rotation.

Messrs. Becker and Fagen gave me some possible reasons for their popularity in a recent interview. "We're doing a kind of music that hardly anybody else, if anybody else, is doing," says Mr. Becker. "We're doing a combination of genres -- harmonic ideas from jazz and rock'n'roll or rhythm-and-blues rhythm sections."

In itself, that's not unique. Everyone from Jimi Hendrix to Van Morrison has married jazz and rock. But Becker and Fagen had the wedding party join in, and most of the guests, too.

The duo absorbed the best of all the musical movements of the 1970s, evoking a range of genres but not settling into any of them. Flitting between genres is all the rage in pop today; Becker and Fagen, however, did more than just juxtapose styles -- they created a new musical language. From disco and jazz fusion came an ultrasmooth, studio-heavy musical surface; from "classic" rock, showy guitars and irresistible choruses; from funk, down-and-dirty licks that still get sampled in rap tunes.

They even imbibed some of the lyrical venom of punk -- in spirit, anyway. Beneath the impeccable chops lurk some of the most biting, and profoundly weird, lyrics in pop. "I like the surface of the songs," says Mr. Fagen, but "there has to be some roughage in there, too, to keep it regular. That's where the blues comes in."

It's not simply the content of the stories that sets them apart -- tales of dwindling hipsters and middle-class losers. The duo's elliptical style made listeners feel as if they were eavesdropping on in-jokes between two old pals. Then there's the ambiguity of intention: You could never be sure if they were snickering at their subjects, like most ironists, or just giving sympathetic nudges.

"To some extent, we're writing for and about ourselves," says Mr. Becker. "If there are barbs, they're probably barbs for us as much as anybody."

The music offered an even bigger ambiguity. Over the years, I have talked with a lot of Steely Dan fans, and all of them marvel at the intricacy of the music -- as lush as a Burt Bacharach score, as flawless and textured as a Brian Wilson arrangement. Yet some are almost apologetic about the smoothness. The songs slid easily into the hot-tub soundtrack of the Me Decade, and were an easy target for Muzak.

I think that's the best joke of all. A lot of artists, from Frank Zappa to the punks, have mocked the slickness of pop, usually by exploding conventions or ignoring them altogether. Becker and Fagen grabbed slickness and made it their own. No band boasted craftier musicians, a cleaner sound or trickier arrangements. They beat pop at its own game, making music so elegant it could be enjoyed by anyone, but so complex only "heads" would absorb the nuances.

"Two Against Nature" continues the tradition. The songs are so funky and danceable, the harmonies so lush, the Yuppie name-dropping so insistent, that it's tempting to simply put the record in the VH-1 box. Then comes the roughage. In "Janie Runaway," a lover considers whisking the young Miss R. to Pennsylvania from Manhattan -- then wonders, "Would that be a federal case?" The hero of "Cousin Dupree," meanwhile, waxes lustful about his aunt's daughter.

It isn't all barbs, though. "Almost Gothic" is one of the band's sweetest love songs, albeit spiked with double-entendre. Other favorites: "Gaslighting Abbie," about a tryst I'm not sure I want explained, and "West of Hollywood," a goodbye to the duo's onetime home -- and the brooding sounds the city inspired.

The album is so much fun, in fact, that it sounds a bit like a love letter to the band itself -- an expression of joy in reviving the "deep mystical soul synergy" after years of working apart. That enthusiasm is clearest in the title song, a samba about two medicine men duking it out with voodoo bad guys.

"`Two Against Nature' is us," explains Mr. Fagen. ("No wonder it's so confusing," Mr. Becker interjects.) "We're sort of casting ourselves as heroic . . . bailing out our fans."

"A `Ghostbusters' ripoff," Mr. Becker observes.

"Yeah," Mr. Fagen says. "Sort of a `Who-you-gonna-call?' deal."

It was a long time coming. But nature never stood a chance.