You would think that Maui or Telluride or Provence might be looking good about now to Harvey Schmidt and Tom Jones. The veteran songwriters are both well into their seventies. They've got plenty of distractions in their lives, Schmidt with painting and writing in Texas, Jones with a wife and teenage children in New York. And certainly they can't be worried about making their mark. They are, after all, the composer and lyricist, respectively, of a show you may have heard of, "The Fantasticks," which last January ended a 43-year off-Broadway run, the longest in theater history for a musical.

But rather than baking on a beach or sipping hot toddies by a hearth, here they were, in a room with a piano in a theater in Arlington, working on, yes, the score of a show. Not a new show, mind you: A 40-year-old show, one that they have always loved, and always felt could have been better.

Having been offered the opportunity by Eric Schaeffer, artistic director of Signature Theatre, to take another crack at "110 in the Shade," they had leaped at it. In preparation for the production, which opens on Tuesday, they fixed a lyric here, redid a lead-in there. Jones, itching to reinforce a theme in the piece that he believed had never been fully realized, wrote a new song for the heroine, Lizzie. He sent the lyrics off to Schmidt in Texas, where the composer sat down and fashioned a melody without changing a single word.

"This just seemed a real chance to try some ideas," Jones explained the other day, relaxing with Schmidt in an office at Signature during a break in rehearsals. "All these ideas sitting in a folder that I'd been building up over the years."

A musical opens, a musical closes. A cast album is recorded, the book and score are published. Fans preserve their Playbills and actors add the title to their re{acute}sume{acute}s. The issue is: Is the show done? Not as in kaput, but as in finished, complete. Is this a work for the ages or a work in progress? Are songs to be rewritten or cut in future productions? Characters rethought, scenes reimagined?

Judging by the attention that many veteran composers and lyricists are lavishing on old projects these days, the families of loved ones lost at sea are not the only group having trouble with closure. Seduced by the prospect of one more pass at perfection, writers of musicals seem compelled to tinker. Stephen Sondheim, for instance, was still tweaking lyrics last year in "Sweeney Todd" and "Sunday in the Park With George" for the Sondheim Celebration at the Kennedy Center. Another of the festival offerings, "Merrily We Roll Along," a flop on Broadway, had been a thorn in the composer's side for years. He has struggled so long and hard with the structure and song placement of the story, which is told in reverse, that no two recent incarnations of the show have been exactly the same.

For the hit Broadway revival of "Cabaret," John Kander and Fred Ebb allowed director Sam Mendes to shift songs around and even substitute numbers from the 1972 movie version. Composer Jerry Herman has been holding out hope for a major new production of "Mack and Mabel," a 1974 cult favorite that has a new book by the sister of the original author. The team that created the 1986 "Rags," Stephen Schwartz, Joseph Stein and Charles Strouse, seems to incorporate changes in virtually every new production of the show. Schmidt and Jones have intimated that even "The Fantasticks" may not be quite there yet.

"All of them will tell you, 'It's never finished,' " said Schaeffer, who has become something of a musical mechanic, poking around under the hood of old shows like "110 in the Shade" and Schwartz's "Working" to see if he can get the engine purring more smoothly. "Maybe it's because musicals are so collaborative, between two or three people, someone is always going to say, 'We could have made this better.' "

In some cases, it's almost as if a composer just can't bear to let go, or more to the point, cannot believe that he's done all he can to ensure that what he leaves to posterity is in the best possible shape. "Steve was, like, 'I think "Sweeney's" finished,' " said Schaeffer, referring to Sondheim's tentative view of his own musical masterpiece, "Sweeney Todd."

Composers are, of course, always looking to the next project: Several of these old masters have works in the wings, including Sondheim ("Gold," premiering at Chicago's Goodman Theatre this spring) and Kander and Ebb ("The Visit," under consideration for the Public Theater in New York next season). A new musical version of "Harold and Maude," adapted from the movie, has lyrics by Jones. (Schmidt opted not to participate.) But to many of these artists, established works seem just as alive as new ones.

This makes sense in a waning age for the musical. The dearth of first-rate young writing talent coming into the musical theater has resulted in the directing of ever more energy toward what's come before. The trend is reflected in everything from the growing popularity of reviving little-known musicals in concert form to the success of the so-called "revisicals," old hits like "Annie Get Your Gun" that undergo wholesale rewrites by new authors to give the productions more appeal to contemporary values and tastes. Not all of these efforts work; a new version of Rodgers and Hart's "The Boys From Syracuse," with a book by playwright Nicky Silver, opened last summer on Broadway to desultory notices.

Of course composers and book writers and lyricists have always been fine-tuning their creations. Jerome Kern and Oscar Hammerstein tried several times to redo the 1927 "Show Boat," the production that heralded the arrival of the modern American musical; Irving Berlin revised "Annie Get Your Gun" in the mid-1960s, more than 30 years before Peter Stone was given the assignment of writing a new Broadway version starring Bernadette Peters.

Still, the pace and the appetite for revisions by the original authors have picked up considerably. In the case of "110 in the Shade," it was Schaeffer's idea to bring it back in a more streamlined form.

The original Broadway production, which opened in 1963 and ran for 330 performances, had a huge cast, which was a stumbling block for Signature's tiny stage.

"I got the script and read it," Schaeffer said, explaining that his interest had been piqued by the number of actors who had auditioned for him over the years with songs from "110," like "Simple Little Things" and "Old Maid." "I didn't want to do it with 55 people, since most of them are merry villagers. So I thought that maybe we could look at reinventing it," he said.

"110" is based on "The Rainmaker," the 1954 romantic drama by N. Richard Nash about a town in the American West, parched by drought, and a man who arrives with the promise of bringing replenishing rain. Nash also wrote the book for the musical, which takes place over the course of a single day, when a local girl, Lizzie, falls for the rainmaker, Starbuck.

It just so happened that Schmidt and Jones had long been thinking about how "110" might be reshaped for a smaller ensemble. "Over the years many times people would come to us and say they wanted to do '110,' 'but we want to do it in a smaller version,' " Jones said. (The Signature production features a cast of 13, including Matt Bogart as Starbuck and Jacquelyn Piro as Lizzie.)

The songwriters arrived at Signature last week to see how things were progressing. Schaeffer was still playing with how to include Lizzie's new number, "You Gotta Get a Man the Way a Man Gets Got." Clearly, Schmidt and Jones were tickled by the working environment. "It's just like college," Schmidt said.

"It's problem-solving," Jones added. "It's a kind of fulfillment, the pleasure of fulfillment of the original piece." After all these years, "110" had not lost its power over him. That was very gratifying to Jones, a very personal kind of endorsement of their decision to tackle the work again. "I can listen to some of these scenes," he said, "and I can choke up."

The opportunity to amend old works offers "a kind of fulfillment," says lyricist Tom Jones.Harvey Schmidt passed on "Harold and Maude," but he was ready to revisit "110 in the Shade."Jacquelyn Piro (with Matt Bogart) will sing the new song written for Lizzie.Harvey Schmidt and Tom Jones are hardly the only composers to tinker with their musical. In 1997, Signature Theatre Artistic Director Eric Schaeffer took another crack at "Working," Stephen Schwartz's 1978 play adapted from Studs Terkel's book, top; Stephen Sondheim tweaked lyrics for last summer's "Merrily We Roll Along," with Raul Esparza, Michael Hayden and Miriam Shor, center; and the songs in "Cabaret" were shuffled for the show's revival, currently starring Neil Patrick Harris, left.