Though known primarily as a country singer, Johnny Cash's music crossed over into folk, rockabilly, blues, gospel, and rock and roll. Known for his husky bass-baritone, he championed the disenfranchised and prisoners, bringing his act to Folsom Prison and San Quentin. These visits were recorded and produced the hits "Folsom Prison Blues," and "A Boy Named Sue." Also known as "The Man in Black," he chose to wear dark clothing on behalf of the poor and hungry, and in mourning of the loss of life in the Vietnam War. Later in life he became an icon of the alternative country movement, and his cover of Nine Inch Nails' "Hurt" proved that there was no limit to his influence or courage in breaking his own mold.