[1] Wallen also co-wrote songs with other artists, including Saint Asonia ("Ghost" and "Beast" off Flawed Design), Love and Death (2021 album Perfectly Preserved), Red ("Sever" from Declaration, "Cold World" and "Our Time Will Come" from Rated R), Pillar ("Call to Action" and "Lose It All" from Confessions), Icon for Hire ("Ready for Combat" and "Shadow", from The Reckoning), We Came as Romans ("Golden" from Darkbloom), Fuel ("Scars in the Making" from Angels & Devils), Dorothy ("Made to Die" from Gifts from the Holy Ghost), Saving Abel ("She Got Over Me" from Saving Abel) and Emmaus Road ("Unbelief" from Transformed).

It included single "Broken Sky" and a song "Call to Action", which was covered and re-recorded by a Christian rock band Pillar for their album Confessions in 2009.

[6] Copper has played more than 300 shows overall, headlining and supporting bands like Thirty Seconds to Mars, Shinedown, Seether, 10 Years, Breaking Benjamin, and Saliva.

During the time with the band, he took part in recording of two albums, Adelitas Way (2009) and Home School Valedictorian (2011), as well as intensive touring and sharing the stage with such notable acts like Guns N' Roses, Creed, Papa Roach, Godsmack, Theory of a Deadman, Three Days Grace, Deftones, Puddle of Mudd, Sick Puppies, Staind, Alter Bridge, Skillet, Halestorm and others.

In 2019, three solo singles were released: two acoustic covers ("Shallow" by Lady Gaga and Bradley Cooper, and "The Look" by Roxette) and one original alternative rock song, "Crows".

Throughout 2020, Wallen posted pictures from the studio on his social media, hinting work on his debut solo full length album alongside Joe Rickard and Jasen Rauch.