[2] Since graduating from Musikhögskolan, where he studied guitar, piano and song, he has worked as a producer and songwriter.

In 2018 he co-wrote the Cypriot entry for the Eurovision Song Contest 2018, Fuego performed by Eleni Foureira which placed second in the competition.

In 2021, he was part of the team that wrote and produced the song "Voices", which won the Melodifestivalen in that year.

He also wrote the official song for the Swedish football team for the FIFA Women's World Cup in 2011.

[citation needed] In 2015, for the Japanese release of the film Avengers: Age of Ultron, Marvel Japan recruited Wrethov to compose an original song,[5] "In Memories", an emotional ballad that also featured in the movie’s Japanese trailers.