With its loud, distorted electric guitars (see entry under 1950s—Music in volume 3), powerful vocals, and often dark style, heavy-metal music became an important style of rock and roll (see entry under 1950s—Music in volume 3) starting in the 1970s. Amid the pop-rock and psychedelic rock of the late 1960s, musicians and groups such as Deep Purple and Led Zeppelin (see entry under 1970s—Music in volume 4) incorporated a harder, louder tone coupled with often mystical imagery that went far beyond anything else heard on the radio (see entry under 1920s—TV and Radio in volume 2) in the late.....
