Colin Marshall talks to documentary filmmaker Nicholas Sherman, director of Soundtracker: A Portrait of Gordon Hempton. Hempton, one of the world’s best-known field recordists, has dedicated his life to traveling the United States and the world to create “sound portraits” of distinctive places. In Soundtracker, Sherman follows Hempton’s road trip in his 1964 VW bus which becomes a quest to capture the sounds of a train and a songbird together.