Deep Purple is an English rock band formed in Hertfordshire in 1968. Together with Led Zeppelin and Black Sabbath they are considered to be heavy metal pioneers. Especially influential to heavy metal were Ian Gillan's powerful screams and Ritchie Blackmore's virtuoso solos. Deep Purple were also very influential to progressive rock. Deep Purple's early output ranged from rock (such as their cover of Joe South's "Hush)" to strongly classically influenced pieces (such as "April", from their third album).