NEW YORK - It's dark, it's gritty, its characters are lowlifes - and after 68 years, the endlessly reworked Pal Joey remains the Play-Doh of musicals. In its fourth Broadway revival, which opened Thursday night, the show has been dressed in yet another updated script. But in the end, it's still defined by its sleazeball title character and his milieu.

The Rodgers and Hart show - about a drifter who runs through women as if they were recyclable, and comes to own a nightclub bankrolled by a rich, older and equally ruthless Chicago siren - was first staged in Philadelphia with an original book by John O'Hara, from a series of epistolary stories he'd written for the New Yorker.

The current Roundabout Theatre production is more a rehab than a revision. If you had seen it in Philly in that 1940 tryout, the new version would be familiar in its look and feel but not in its particulars. Playwright Richard Greenberg (Take Me Out, Three Days of Rain) scraps some old-hat, back-alley '30s talk as well as some of the plot's nuance. He updates the way the story moves, cutting much original detail and in the process giving its characters new ways to express their seediness. In one important scene, even the premise of a blackmail threat is reworked and updated.

Normally, it's forbidden to alter a script unless you're the author - and even then, there's a limit; the theater phrase "freezing a script" means the production's rehearsals have reached an artistic point of no return, at least for the actors' lines, so the playwright can't meddle, at least until the next production.

Pal Joey, though, seems to have been a constant work in progress. Several years ago, Bert Fink, the spokesman for the owners of the rights to the show, the Rodgers & Hammerstein Organization, told a reporter that "there were so many alternate versions that we had people saying, 'We want this from Column A and that from Column B.' "

Greenberg's new book gives Joey, his society sugar mama (a dead-on Stockard Channing), and even the play's one decent character - the girl who wants to believe in his potential as a long-term catch - glib repartee that's more like a laugh-line thread than comic relief.

Joe Mantello's direction (he owns Tonys for staging Assassins and Take Me Out) accentuates this characteristic of the revival - nasty talk with a chuckle. Matthew Risch as Joey, the terrific Martha Plimpton as showgirl Gladys Bumps, Jenny Fellner as Linda, the nice girl, and Channing's Vera take it up with zest for the bon mot that's really more mauvais mot.

Try this new, more overtly sexual dialogue with smirky Joey, out to charm rich, reluctant Vera into footing the bill for his existence.

Vera: When you stopped by uninvited last night - never do that again, by the way - it reminded me that life can be -

Joey: Richer and fuller? (She slaps him but he doesn't respond.)

Joey: May I come home with you tonight?

Vera: Well, since you said "may I" - my car is waiting right outside.

The script is full of such stuff, and while Pal Joey traditionalists may take offense at the changes, Greenberg's back-and-forth hints that these characters could be likable, even though the show still generally operates in the shadows. "Can you draw sweet water from a foul well?" asked critic Brooks Atkinson when Pal Joey first opened. The answer was no then, and it's still no. But Greenberg's vibrant book makes the water a little less brackish.

It's also no theatrical sin that this most malleable of musicals has been rethought and, in a sense, re-created. After it opened in Philadelphia, it was reworked before reaching Broadway - the usual process at the time - and made Gene Kelly famous. Then it was revised for its first Broadway revival in 1952, which made Elaine Stritch famous.

Five years later, heavily revised by Hollywood, the film version didn't make anyone famous - Frank Sinatra and Rita Hayworth already were, and Kim Novak was no slouch, either. In 2002, Philadelphia's Prince Music Theater revived it in Center City in its rarest form - using the original Philadelphia-tryout, pre-Broadway script.

Pal Joey contains two songs that escaped the show into mainstream popularity. One was "I Could Write a Book," the other "Bewitched, Bothered and Bewildered," whose path to becoming a standard mirrors the show's own evolving journey. The song, Vera's almost-self-loathing reflection of her lusty fall for Joey and her loose values in general, was completely desexed to become an acceptable hit. Channing's smoky, earthy delivery of the real lyrics is the show's highlight - as is Channing herself, sealing the deal each time she enters a scene.

Moving this revival forward has been tough for the Roundabout, the Broadway nonprofit that over the years has triumphantly revived notable American musicals as part of its mission. The original Joey, Christian Hoff, injured his foot in previews last month (the production is choreographed by Graciela Daniele - brazenly, at one point, on stairs) and had to withdraw.

Understudy Matthew Risch, in one of those Broadway dream-come-true moments, took over the role and delivers a respectable performance. An ensemble player in Legally Blonde and Chicago, he is a talented dancer and a strong singer. His Joey displays an arrogance as threatening as it is magnetic, and his lizardlike smile reminds that some things in Pal Joey must never change.

Contact staff writer Howard Shapiro at 215-854-5727 or hshapiro@phillynews.com. Read his recent work at http://go.philly.com/howardshapiro.

Presented by Roundabout Theatre at Studio 54, 254 W. 54th St., New York.

Tickets: $36.50-$126.50. Information: 212-719-13009 or www.roundabouttheatre.org. EndText