There are younger bands than the Rolling Stones. There are more original bands. There are crazier bands, funkier bands, smarter bands. Live, there are any number of tighter bands. But for all the challenges the Stones have fielded in their 14-year recording career - from Aerosmith to the Sex Pistols - their superb new album proves that the Stones are still the undisputed masters of mainstream rock 'n' roll.

The Stones have found their place as the world's leading high-society lowlifes. One moment they're lifting pinkies - the next, they're lifting skirts. What began as a rude, hungry quintet of blues enthusiasts has evolved into a quintet of rude, ironic rock 'n' rollers whose last few albums have been sustained by image rather than music, as Mick Jagger has made the rounds at posh parties and Keith Richards has gone through a drug-related legal roundelay. (Going to court, Richards has said, is "just an expensive habit.") With "Some Girls" (Rolling Stones/Atlantic COC 39108), however, the Stones sound rude and hungry again. It's a welcome reminder that they are musicians first of all, not celebrities.

"Some Girls" flaunts riffs the Stones have used countless times. Rhythm guitars out of Chuck Berry, drum thumps from Chicago blues, country-flavored lead guitar, vocals in the peculiar London slum/deep South accent that only Mick Jagger speaks - none of these is new. (The album cover, with the Stones in various forms of drag, is an old joke, too.) And they had tried all of the musical styles - disco, country, rock 'n' roll. Motown - on other LPs. On paper the album sounds like a rehash. On the stereo, "Some Girls" is a triumph.

"Black and Blue" (1976), their previous studio LP, experimented with a disco beat while auditioning lead guitarists (ex-Face Ron Wood eventually accepted the spot), and its groove songs were aimless. "Love You Live" (1977) sounds lazy compared to earlier live Stones discs. To find a Stones album with the same vitality as "Some Girls," it's necessary to dig out "Exile" and "Some Girls" are sloppy and belligerent; both of them, despite the mature Stones' self-consciousness, rock with a vengeance.

Sloppiness is the key. The songs on "Some Girls" inhabit a jungle of guitar tracks; most cuts have both Keith Richards and Mick Jagger playing rhythm while Wood alternates among rhythm, lead and pedal steel guitars. Sometimes lyrics are lost, but it hardly matters. If anyone other than Jagger and Richards - the "Glimmer Twins" - had produced the album, many of the guitar tracks would have been eliminated, vocals would be out front, the rhythms would be simple and uncluttered. And the album would sound like any other album. As it stands, the loose ends and oddball mixes make "Some Girls" sputter with life.

Each song, furthermore, has a distinct ambiance: full-bodied country rock in a remake of the Temptations' "Imagination": an insistent midrange throb in "Shattered"; earnest drive in "Before They Make Me Run." While there are resemblances to earlier Stones songs, especially among the rockers, the production never allows them to be as close as, say, "Jumping Jack Flash" is to "Street Fighting Man." Better yet, the playing and singing are joyously aggressive. Drummer Charlie Watts boots the backbeat, and the three guitars interwine tight as a noose. Jagger's lead vocals are wild; in "Shattered," he takes some phrases all the way into the animal kingdom.

Not that he's really shattered, of course. He's posing, and his swaggering burlesque tone encourages you to laugh along. Although "Some Girls" was largely recorded in Paris, most songs mention New York, and the album has a distinct N.Y.C. sensibility: Party now, because everything's falling apart. The Stones haven't revealed their humorous side in years; maybe it took exposure to the Big Apple to stimulate their jaded sensibilities. Whatever the reason, Jagger's obviously laying down a line of jive in the disco single "Miss You," and the ethnic sexism of the title cut is so funny that even those who never forgave Jagger/Richards for "Under My Thumb" will chuckle. The band, with Ron Wood's boozy slide and steel guitars, also seems to be amused and having a great time.

Hidden in the middle of Side Two is the album's one serious song "Before They Make Me Run." It's Richards' only lead vocal on the LP, and it sounds autobiographical: "Booze and pills and powders/You got to choose your medicine." Jagger's in control when he sings, but Richards is not: his voice is weak, quavery, scary.It reminds you of what's going on behind the party: If Richards can't beat his drug rap, the current Stones tour will be his last, and "Some Girls" could conceivably be his last album. Richards is the mainspring of the Rolling Stones, the rhythm that drives the whole band. Hearing his voice makes you wonder where he got the strength to work out the album's brilliant guitar parts.

"Some Girls" is a conservative album. But it conserves the best aspects of the Rolling Stones' music: the unstoppable beat, the lewdness, the comedy and the danger. The Stones have returned to their own tradition of taking chances - at a time when band after band plays it safe, the Stones do their best to be unpredictable. That alone is reason to be grateful. Beyond that, "Some Girls" is good reason to dance.