MASTER OF REALITYThe shortest album of Black Sabbath's glory years, Master of Reality is also their most sonically influential work. Here Tony Iommi began to experiment with tuning his guitar down three half steps to C#, producing a sound that was darker, deeper, and sludgier than anything they'd yet committed to record. (This trick was still being copied 25 years later by every metal band looking to push the limits of heaviness, from trendy nu metallers to Swedish