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story.lead_photo.caption Recording artist Ed Sheeran performs onstage during The 59th GRAMMY Awards at STAPLES Center on February 12, 2017 in Los Angeles, California. (Kevork Djansezian/Getty Images/TNS)

Ed Sheeran's new album grew out of the fact that he really didn't need any more alone time.

Arguably the most successful male pop star in the world, Sheeran nonetheless tours like a lonely street busker, with just his guitar and a digital looping pedal to accompany his voice, even when he's selling out multiple nights at gigantic stadiums like London's Wembley.

So when the 28-year-old English singer began work on his follow-up to 2017's Grammy-winning "," he figured it might be nice to have someone to talk to for a change.

"It was kind of informal," said Ed Howard, managing director of Sheeran's U.K. label, Asylum, who oversees the making of his records along with Atlantic U.K. president Ben Cook. "He's on tour and somebody he loves comes through to see the show—maybe they end up writing a song together.

If that casual process suggests a collection of larks, think again. On "No. 6 Collaborations Project," due today, Sheeran convenes some of pop's biggest names—including Cardi B, Justin Bieber, Travis Scott, Eminem and Bruno Mars—for an album as precisely rendered as any Sheeran has made.

There's Caribbean-accented dance-pop, glowing R&B balladry, even a Sunset Strip hair-metal jam—enough variety to lead Howard to say, "I don't think there's anybody else in the world that could make credible music with this range of artists in this many styles."

In South America he got turned on to Paulo Londra, a young Latin trap phenom from Argentina, who guests on the track "Nothing on You." And in Nashville he and Chris Stapleton, the burly country singer, got the ball rolling on a song that eventually became the hard-rocking "Blow," which also features Mars. (Sheeran's original idea for the similarly flexible Mars, Cook said, was "this kind of 'Lady Marmalade'" that would have teamed the two with Bieber, who instead ended up dueting with Sheeran on the album's lead single, "I Don't Care.")

"Best Part of Me," a duet with up-and-coming soul singer Yebba, is an outlier on "No. 6"—"more of a traditional Ed Sheeran song."

Other featured guests include Ella Mai, Camila Cabello, H.E.R., 50 Cent, Meek Mill, Young Thug and Khalid, the last of whom helps open the album with "Beautiful People."