April MacLean mostly played folk music on the violin. Charlie Smith didn't know what it was, so he looked it up on his mobile phone, and wondered why, in the video, they were all dancing in a circle. (TV: The Coach with the Dragon Tattoo)
By the time of the twentieth century, there had been centuries of a genre of folk music called "night visiting", which were songs about spirits of deceased loved ones that would knock on their living relatives windows at night and appear to them, sometimes as a warning of danger and other times to drag their living relative to Hell with them. (TV: Nightvisiting)