Vol. 4 was Black Sabbath's most experimental album at the time of its release. They had taken their signature heavy sound and refined it on tracks such as "Supernaut" and "Tomorrow's Dream". They took a more sensitive approach on the hit "Changes", a piano ballad with heartbreaking lyrics about drummer Bill Wards split with his wife. Vol. 4 was ranked number 14 on Rolling Stone's "100 Greatest Metal Albums of All Time".
