To stand out in a sea of singer-songwriter wannabes and to be a trailblazer in the genre, a person's vocals must sound wholly organic. In Iris DeMent's tone, there's screeching and wildness but also a purity. She always tried to emulate her mother's voice and also the preacher's wife from her hometown church. When she sits at the piano, she says she does her best to let "something ancient and spirit-filled come through [her] and move around the music." Expect her to tap into those emotions for tonight's show. (Laura Morrison)