He then made the switch to the tenor saxophone and worked with local bands in Visby, Borås and Gothenburg, going to Stockholm in 1954 to join the Simon Brehm orchestra.
From 1956–1957, Billberg was performing in various American clubs located in Germany and France with vibraphonist Vera Auer.
In 1966, he joined the Danish Radio Big Band (led by Ib Glindemann), spending the summer in Gothenburg helping to look after his mother's hotel in the city.
The liner notes to the CD Rare Danish Recordings 1956-1957 states that:According to the most credible jazz witnesses in Denmark and Sweden...Billberg was an extroverted artist with a gluttonous appetite for life and all it has to offer – including intoxicants, which came to affect both his emotional and physical health - but never stopped his love of playing in all tempos and keys.
[2] Music broadcaster Peter H. Larsen has drawn comparisons between Billberg's lyricism and that of Lee Konitz.