In 1966, Hansson saw American jazz organist Jack McDuff perform at Stockholm's Gyllene Cirkeln Club, and was so captivated by the performance that he decided to leave The Merrymen to expand his musical horizons. Encouraged by fellow Merryman Bill Öhrström, he eventually acquired his own Hammond organ. Öhrström became an A&R man and producer at Polydor Sweden, and introduced Hansson to other musicians, one of whom was drummer Janne Carlsson. Hansson and Carlsson immediately hit it off and were signed by Polydor under the band name Hansson & Karlsson, playing up-tempo Hammond organ based music and releasing three albums between 1967 and 1969. They became immensely popular in their home country and some parts of Europe, and even reached the ear of Jimi Hendrix, who took time out from his tour to jam with the duo, along with George Clemons on drums and Georg Wadenius on guitar, at the Klub Filips in Stockholm in late 1967. Hendrix went on to record a Hansson song, "Tax Free". "Tax Free" appears on War Heroes, South Saturn Delta, and various live bootleg recordings.