Who Is Shellback? Get To Know Taylor Swift's Longtime Collaborator

We don't think we need to tell you about how huge Taylor Swift's album rollouts are ... unless you've been living under a rock for the past few years!

The thing is, the hitmaker's albums usually aren't just solo affairs, and she's built up a cool little group of collaborators she goes to for help with production and instrumentation -- including Karl Johan Schuster, a songwriter and producer known professionally as Shellback.

We're going to take a look at his background and see how he went from playing rock music to writing some of the biggest modern pop tracks in the world.

Shellback's originally from Sweden, and he made his bones as a vocalist and multi-instrumentalist in the country's well-known heavy metal scene.

The performer provided vocals for death metal band The Blinded's 2007 album "Bedtime Prayers," and he played various instruments for several Swedish groups over the course of the 2000s, according to Discogs.

Shellback eventually began collaborating with Max Martin -- who's got a history of his own with Swift -- and started working in the pop music scene as a producer and songwriter.

He racked up a healthy amount of hit tracks as a co-songwriter in the 2010s -- like Pink's "Raise Your Glass" and Maroon 5's "Moves Like Jagger" ... long story short, the guy's got a knack for writing catchy tunes.

Shellback began working with Swift in 2012, and he helped write the smash hit tracks "We Are Never Ever Getting Back Together," "I Knew You Were Trouble," and "22" ... all of which were featured on her album "Red," which he co-produced.

The producer became one of the singer's frequent collaborators, and they worked together on numerous occasions over the course of the decade.

The musician was listed as one of the several co-producers who worked on Swift's re-recorded versions of "Red" and "1989."

Shellback also earned himself a total of four Grammy Awards -- including the Album Of The Year award for his work on Adele's 2015 record "25" -- and numerous nominations for his work as a songwriter and producer.

Although Shellback and Swift didn't collaborate on her later albums "Midnights" or "The Tortured Poets Department," she kept in contact with the musician, and he was revealed to have been one of the producers of her twelfth record, titled "The Life Of A Showgirl."

The singer spoke about her work with the songwriter during an episode of the "New Heights Podcast" -- cohosted by her boyfriend Travis Kelce -- and claimed she, Shellback and Martin, were "carrying the same weight as creators" working on the new record.

Swift described the recording process as "really special" and said the trio wanted to "bring the best ideas we’ve ever had" to the studio.