Born in Stockholm and got hooked on New Orleans music after hearing Bunk Johnson on the Decca, W.73149-B-De 25132, at the age of eleven. That really turned him on, and he started on cornet at the age of l4, on a borrowed horn.
Participated on the Stockholm trad jazz scene in the early 60s in different groups. Gave up playing regularly in the middle of the 60s due to university studies. Moved north in the beginning of the 70s, met buddies from the old days and started to play again.
Co-founder of Barfota Jazzmen in the middle of the 70s and is still sitting in the middle of the frontline. Also founder and President of the Swedish Bunk Johnson Society and a devoted researcher and writer on the subject of jazz.
In 1997 Claes was awarded The Armstrong Prize for his research on early jazz.
Claes is also a keen collector of instruments from the golden period of jazz. In his collection you can find a Conn cornet from 1915, similar to the one used by the legendary Freddie Keppard.