John R. Cash was an American singer-songwriter. Most of his music contains themes of sorrow, moral tribulation, and redemption, especially songs from the later stages of his career. He was known for his deep, calm, bass-baritone voice, the distinctive sound of his backing band, the Tennessee Three, that was characterized by its train-like chugging guitar rhythms, a rebelliousness coupled with an increasingly somber and humble demeanor, and his free prison concerts. Cash wore a trademark all-black stage wardrobe, which earned him the nickname "Man in Black".