shellback

Max Martin and Shellback, Swedish pop wizards who’d helped her expand her sound in hits such as “We Are Never Ever Getting Back Together,” returned for “1989” as part of a crew that also included writer-producer Jack Antonoff, who’s gone on to become perhaps Swift’s closest studio collaborator.

Swift wouldn’t score her first No. 1 single on Billboard’s Hot 100 until “We Are Never Ever Getting Back Together,” from 2012’s “Red” — an album for which she consciously adopted the sleek programmed textures of the hitmaking pop producers Max Martin and Shellback.

That’s the message from “Never Gonna Not Dance Again,” an explosion of pop she wrote with hitmakers Max Martin and Shellback, with a video of Pink roller-dancing through a supermarket.

“Shake It Off,” written by Swift and the producers Max Martin and Shellback — who were also defendants in the case, along with the record companies and music publishers associated with the track — features a chorus that her fans can chant by heart:

Working with a varied cast of studio pros including DJ Dahi, Babyface, Benny Blanco, Shellback, Rodney Jerkins, Carter Lang and ThankGod4Cody, SZA paints a detailed portrait of millennial insecurity.