Halfway through a year filled with new work from some of the most popular artists alive, the best-selling album is the soundtrack to a Hugh Jackman movie musical that never led the box office.

"The Greatest Showman" has sold almost 4 million copies for Atlantic Records, outpacing works from Kanye West, Taylor Swift and Justin Timberlake. Music from the film, based on the life of circus promoter P.T. Barnum, has outsold the next-most-popular album of the year, Post Malone's "Beerbongs & Bentleys," by about 2-to-1.

Top-selling original soundtracks are a rarity these days, even if record labels are devoting more attention and energy to the once-neglected genre. "The Greatest Showman," with songs by Zendaya and Zac Efron, has become the best-selling soundtrack since "Frozen" in 2014, according to Warner Music, which owns Atlantic.