They're getting there. They're still in transit, but they're getting there.

They are librettist Joseph Stein, composer Charles Strouse and lyricist Stephen Schwartz, and their aim is to tweak, polish and revise their 1986 Broadway musical, Rags, until they get it right. Rags, you see, perished in New York after a mere four performances, scarcely a fit end for a musical about the promise of America. And so, through a string of resident-theater revivals that began in 1991, the creators continued to fiddle with the show.

Their latest version is on view at the Walnut Street Theatre in a first-class production directed by Bruce Lumpkin, and if it doesn't reveal Rags as a neglected masterpiece, it at least stakes an arguable claim to a place in the repertory. True, despite the trimming and focusing of the last decade, Rags still encompasses more plot than it can accommodate. Yet a surfeit of ambition is surely preferable to a paucity, and in any event the show has a number of compensations.

Attempting nothing less than a summary of the Jewish immigrant experience in America, Rags revolves about one Rebecca Hershkowitz, a young Russian wife who arrives at Ellis Island in 1910 with her small son and finds work in a sweatshop while living in a Lower East Side tenement with her shipboard friend, Bella, and Bella's dictatorial father. Rebecca is soon touched by the nascent labor movement, embodied by the fiery labor organizer Saul, to whom she's attracted even as she continues to hunt for her husband, who emigrated six years earlier.

Subsequent events, which include not only the notorious Triangle Shirtwaist Co. fire of 1911 but a visit to Tammany Hall, are not entirely unpredictable. Yes, the story is a familiar one, yet the principal characters nonetheless emerge in sufficiently distinct outline to make you care about them. (A first-rate cast, headed by Betsi Morrison as Rebecca, Mary Kate McGrath as Bella, Bruce Winant as Bella's father, and Michael Gruber as Saul, has a lot to do with this as well.) And yes, it is not without its sentimental aspects, but then what's a good Jewish repast without a healthy dollop of schmaltz?

It does wander a bit, however, especially during a detour into a Yiddish-theater version of Hamlet; and, as noted, it's probably all a bit too episodic for its own good. Still, the only part of the show that really doesn't work is the deployment of four snooty swells in white evening dress, billed only as "Americans," who pop up now and then to sing or sometimes just to be. The idea is a good one, but it's insufficiently developed, and the figures' symbolic identity (are they all Americans, or just some?) is unclear.

Whatever the book's failings, though, the score goes a long way toward ameliorating them. Strouse's music begins in two separate modes, the Old World strains of the immigrants and the ragtime of the Americans, and then sneakily starts to meld them, sometimes (as in the title song) with deliberate tension. As the evening progresses, other genres (a blues, a waltz, a march) appear, though the predominant influence remains the rag. This is splendid stuff, and while Schwartz's lyrics aren't quite on the same level, they're never less than serviceable and often pointed or clever.

Lumpkin's staging keeps the evening smartly on the move; John Farrell's brick-walled unit set efficiently becomes everything from a sweatshop to a Lower East Side street; and the production's costumes, lighting, and music direction are fine as well. Rags is the sort of musical that keeps reminding you of other shows: A cute old folks' love song mirrors one in Cabaret; a political satire calls up Fiorello!, and the evening as a whole persistently recalls Ragtime, which deals with the same period and is better in every respect. Yet if some of Rags' designs are knockoffs, its workmanship is generally solid. I think you'll find it a comfortable fit.