[1] Belli's debut as a singer was in 1959, for a band called Trefters.

In the 1960s, he became Denmark's first rock star, alongside his band, Les Rivals, warming up for such greats as The Rolling Stones and The Beatles.

In the 1970s, Belli transitioned to doing more dansktop, having several hits such as Bliv væk fra vort kvarter and Ingen regning.

In the same period, he started acting in a number of Danish movies.

In the late 1980s Belli returned to his rock roots, having great success with his Yeah album.