The Barry Manilow musical “Harmony,” now gearing up for a regional nonprofit co-production that will play Atlanta and L.A. next season, has been an on-again, off-again Broadway contender since it bowed at the La Jolla Playhouse in 1997 — mostly off-again, since a planned 2004 New York berth failed to materialize.

But the B.O. success of Manilow’s recent Main Stem concert engagement looks poised to reawaken commercial curiosity about the title.

“Manilow on Broadway” wowed legiters earlier this year with sales figures that were so strong they prompted a two-week extension, adding up to a 27-perf engagement grossing a total of $4.2 million (and in its final week, $910,000 from just five shows). Clearly there’s commercial potential in the overlap between the musician’s fanbase and the older-skewing demo of Broadway ticketbuyers.

That fact alone is likely to send more than a few Gotham producers down to Atlanta’s Alliance Theater, where the new production of “Harmony” opens the theater’s 2013-14 season Sept. 6.

Whether it’ll kickstart a commercial trajectory for the title, however, remains another matter.

There’s a significant difference between generating strong sales in a limited, low-cost concert engagement and sustaining long-term box office for a new musical in which Manilow doesn’t even appear. He pens the music for “Harmony,” with book and lyrics by his longtime collaborator Bruce Sussman.

A score by a musician with an ardent following doesn’t guarantee boffo numbers for a musical. For proof, look no further than the so-so sales of 2009 tuner “9 to 5,” which boasted new songs by Dolly Parton. Current Broadway musical “Hands on a Hardbody,” with tunes by Phish frontman Trey Anastasio, also has yet to set the box office on fire.

The 2010 musical “American Idiot,” with music by Green Day, logged generally healthy sales but didn’t quite recoup after a bit more than a year on the Rialto. B.O. only really spiked during those limited weeks when Green Day frontman Billie Joe Armstrong performed in the show.

With all that in mind, any producers checking out “Harmony” will be looking to see if the show — retooled in the years since it premiered, according to Alliance a.d. Susan V. Booth — is strong enough creatively to back up any anticipated enthusiasm from Manilow fans. Storyline centers on the Comedian Harmonists, a six-man singing group that rose to popularity in 1930s Germany before the ensemble’s mix of Jews and gentiles made it a target for the Nazi government.

For now, no commercial producers are attached to “Harmony,” co-produced by the Alliance and Center Theater Group in L.A., where the tuner is set to play a run that begins March 5 at the Ahmanson.