Berglund was familiar with Swedish folk music as well as with pop and rock music. At the age of ten he started playing rock guitar, but later changed to bass guitar. As part of his musical training at the Birka Folkhögskola in Östersund he came to pick up the upright bass and played in the regional symphony orchestra, with whom he also had guest performances and first television appearances. In 1990 he moved to Stockholm to study at the Kungliga Musikhögskolan. There he played in the group Jazz Furniture and in the quintet of Lina Nyberg, where he met Esbjörn Svensson.
From 1993 he was a member of the highly successful Esbjörn Svensson Trio, with whom he recorded numerous albums and toured worldwide. He was a member of the trio until the death of Svensson in 2008. In 2009 he founded his own crossover band Tonbruket, which includes Johan Lindström (guitar, keyboards), Martin Hederos (piano, accordion, violin, keyboards) and Andreas Werliin (drums, percussion), who do not come from the jazz scene. The band's 2009 debut album was awarded a Swedish Grammy.[1]