Karl Martindahl had his debut in the TV program Söndagsöppet in the early 1990s as a child singer with "The Flying Eagles" and the song "Filippa".

In 2004, he took part in Melodifestivalen 2004 with "Love Turns Water into Wine" written by Michael Persson and Peter Broman a bid to represent Sweden in the Eurovision Song Contest 2004, but failed to be chosen.

In 2004, agreed with Johan Becker, the Fame Factory winner in 2004[1] to form the pop duo The Wallstones where they had a 2005 album Pleasure and Pain and three singles "Good Old Stonecake" in 2004, and "C'mon Julie" in 2005.

The Wallstones duo made another bid to Melodifestivalen 2005 with "Invisible People" written by Martindahl and Becker, but didn't make it to the final of the contest.

Karl Martindahl is now a lead singer with the band Charlie Emm, that also includes Ryan Roxie (the former guitarist with Alice Cooper).