John Fahey grew up in suburban Maryland, in the fifties, when musicians like Rosemary Clooney were at the top of the charts. He gravitated in another direction, toward blues and roots music, and adapted techniques from those musical styles into a genre now known as fingerstyle guitar. Though he became one of the most influential and innovative guitarists in American music, he was wracked by anxiety and lived in obscurity and squalor. Nicholas Thompson, the editor of newyorker.com, is an avid fingerstyle guitarist and Fahey fan. He spoke with Steve Lowenthal, the author of “Dance of Death: The Life of John Fahey, American Guitarist,” about Fahey’s life and work.