She describes herself as "Bronx Jewish white," a lyricist best known for country music hits like the Grammy-winning "Break It to Me Gently."

He's a "southern black Tallahasseean," a jazz cornetist and composer with tunes like "Work Song" to his credit.

She always knew her dream would come true. He thought so, too, but now, after 15 years of working together, they scarcely believe it's happening.

Both agree it's hard to tell just what they have in common, musically or otherwise, but Diane Charlotte Lampert and Nat Adderley are sure of one thing: collaborating on the Broadway-bound musical "Shout Up a Morning," which opens at the Kennedy Center's Eisenhower Theater tomorrow, has been a labor of love that has verged at times on obsession.

"It's my soul," says Lampert, who actually began working on "Shout," a show based on the folk legend of the railroad-spike-driving John Henry, 25 years ago with composer Peter Farrow.

"If I die today and they cut me open, they wouldn't find a heart beating. They'd find a steam engine," Lampert says with a laugh. "The show is my dream and you don't give up on dreams . . . it's been hard at times. What do you tell people every day when they ask what's new? You tell them about 'Shout Up a Morning'? -- you lose a lot of friends that way. But I never gave up on it. Never."

Curiously enough, for someone who admits the show has nearly consumed her life at times, Lampert says she wasn't immediately drawn to the project. At first, she found it difficult to relate to the John Henry legend, thinking it had more to do with the black experience than her own. But that was before she discovered the show's universal "I realized that this is really a story about man versus machine, and that's when I became hooked," she said, a thick Bronx accent still very much evident. "And I think, looking at unemployment and automation and everything, we still see that kind of thing, that same kind of struggle happening today."

Adderley entered the picture 15 years ago, after his brother, the late saxophonist Cannonball Adderley, agreed to compose the music for the show. The brothers ordinarily worked as equals on their collaborations, mostly compositions for their own band. But on this assignment -- the first time the two had composed music for lyrics already written -- things were different.

"This was Cannonball's baby," says Nat. "He was the quarterback, calling all the shots. He would send me the book with the sections I was supposed to write music for marked off. We worked independently."

Like Lampert, Nat Adderley had his reservations at first. "To be honest," he recalled, "when I first saw the book, I thought, what's Cannon talking about? Looking at the words and all. But after I got into the lyrics and the storyline and realized how melodies could fit in here and there, it became a very interesting project."

And a long one. The brothers worked on the music for a couple of years in between their performances, an effort that culminated in the release of an album called "Big Man." (The temporary name change was a tribute to Cannonball's heft and involvement, says Lampert.) But Cannonball died just before the release of the album in 1975, without ever seeing the show produced.

"The last time I saw Cannonball," recalls Lampert, "was before he had his stroke. He said to me, 'I've done everything I can, and I'm putting it in your hands now because I know you're going to get this show on one day.' He believed it would happen, too."

It wasn't until after Cannonball's death that Lampert and Nat finally met. Last April, with a corporate assist from AT&T (which is helping to underwrite the production) and the directorial guidance of Des McAnuff ("Big River") the two began to revise the show, adding new songs, deleting others.

For Lampert, working with the Adderleys has been a joy. "I don't know a note of music," she says, "so I don't have any limitations. I've written lyrics for all kinds of music. I even did something for Ravi Shankar, so getting hooked up with Cannonball was kind of natural."

For Nat Adderley, working on "Shout" has, among other things, allowed him to explore some of his early nonjazz influences, including much of the folk and gospel music he heard growing up in the South. It also means he'll be missing the lucrative festival season overseas, where he is frequently showcased working with either his own band or in some all-star setting.

"But I'm not complaining," he says, noting that the response "Shout" received when it previewed last month at the La Jolla Playhouse was reward enough.

"When you hear applause like that, you feel you are really contributing something. It's just a marvelous feeling."