When the North American tour of Disney Theatrical Prods.’ stage musical “Newsies” opens in Philadelphia tonight, it’ll have something its Broadway audience didn’t see during the show’s two-and-a-half-year run in New York: A brand new song.

It’s not all that unusual for a road production to incorporate minor changes that creatives had wanted to make in the Broadway version but never got the chance. But the new tune in “Newsies,” “Letter from the Refuge,” wasn’t one of those. It originated in an off-the-cuff brainstorming session that unexpectedly yielded an idea that was a keeper — a year after the musical opened on the Main Stem.

In a March 2013 episode of the American Theater Wing series “Working in the Theater,” shown at the time on public access cable (and now available digitally), DTP president and producer Thomas Schumacher challenged “Newsies” collaborators Alan Menken and Jack Feldman to write an additional song for the show. It was just an exercise, intended solely as a way to illustrate how new tunes are created.

Feldman came up with an idea for a new song for Crutchie, the disabled newsboy who halfway through the show is snatched away to a juvenile detention center. The song would depict Crutchie in the refuge writing a letter to his friend Jack, the musical’s protagonist. In the “Working in the Theater” episode, called “The Anatomy of a Song,” Feldman riffs on a few lines and lyrics that occurred to him while Menken noodles away at some underscoring.

Feldman recalled, “When we were done, both Alan and Tom said to me, ‘Let’s do it for real!'” Part of the appeal was the fact that the addition would turn a second-act spotlight on a central character who, once he’s sent away, isn’t otherwise seen until the end.

For his part, Menken — currently at work on Disney’s retooled stage version of “The Hunchback of Notre Dame” — said the music he ended up with doesn’t sound a whole lot like that initial underscoring he tried out, but the tone is the same.

“Crutchie as a character would never be self-pitying, and he’s not used to writing letters, so that defined the pace and the tone of the song,” Menken said. “It’s tentative, emotional but guarded, with a sense of false bravado and a tenderness underneath. For other songs in the show, for instance,  I wanted to give ‘Carrying the Banner’ kind of a honkytonk feel, and ‘Seize the Day’ has a military sound. But this one is really just the music of the heart, so we wanted to keep it quiet and tender.”

Feldman aimed to keep the tune simple, a solo song with minimal set requirements, thereby making it easy to fold in to the preexisting second act. “There’s a bed,” he said of the furniture the number ended up requiring. “Although I honestly don’t know what’s under the sheet. It could be a printing press, for all I know!”

The song debuted Oct. 11 at the tour’s first stop in Schenectacy, which over a full week pulled in more than $1 million at the B.O. The touring production officially opens tonight in Philadelphia, with stops to follow in Chicago, Miami, L.A. and Vegas, among other cities.