Editing British blues (section)

==Decline==
[[File:Jethro-Tull-cropped.jpg|thumb|left|Members of [[Jethro Tull (band)|Jethro Tull]], in 1973, by which time they had already begun to move away from a blues sound]]
British blues entered a rapid decline at the end of 1960s. Surviving bands and musicians tended to move into other expanding areas of rock music. Some, like Jethro Tull, followed bands like the Moody Blues away from 12-bar structures and harmonicas into complex, classical-influenced [[progressive rock]].<ref>S. Borthwick and Ron Moy, ''Popular Music Genres: an Introduction'' (Edinburgh: Edinburgh University Press, 2004), {{ISBN|0-7486-1745-0}}, p. 64.</ref> Some played a loud version of blues rock that became the foundation for hard rock and heavy metal. [[Led Zeppelin]], formed by Yardbirds guitarist Jimmy Page, on their first two albums, both released in 1969, fused heavy blues and amplified rock to create what has been seen as a watershed in the development of hard rock and nascent heavy metal.<ref>C. Smith, ''101 Albums that Changed Popular Music'' (Madison NY: Greenwood, 2009), {{ISBN|0-19-537371-5}}, pp. 64-5.</ref> Later recordings would mix in elements of folk and mysticism, which would also be a major influence on heavy metal music.<ref>S. T. Erlewine, [http://www.allmusic.com/artist/led-zeppelin-p4739/biography "Led Zeppelin: biography"], ''Allmusic'', retrieved 8 September 2011.</ref> [[Deep Purple]] developed a sound based on "squeezing and stretching" the blues,<ref>P. Buckley, ''The Rough Guide to Rock'' (London: Rough Guides, 3rd edn., 2003), {{ISBN|1-84353-105-4}}, p. 278.</ref> and achieved their commercial breakthrough with their fourth and distinctively heavier album, ''[[Deep Purple in Rock]]'' (1970), which has been seen as one of heavy metal's defining albums.<ref>E. Rivadavia, [http://www.allmusic.com/album/deep-purple-in-rock-r187662/review "Review: Deep Purple, In Rock"], ''Allmusic'', retrieved 29 December 2011.</ref> [[Black Sabbath]] was the third incarnation of a group that started as the Polka Tulk Blues Band in 1968. Their early work included blues standards, but by the time of their second album ''[[Paranoid (album)|Paranoid]]'' (1970), they had added elements of modality and the occult that would largely define modern heavy metal.<ref>M. Campbell and J. Brody, ''Rock and Roll: an Introduction'' (Cengage Learning, 2nd edn., 2008), {{ISBN|0-534-64295-0}}, pp. 213-4.</ref> Some, like Korner and Mayall, continued to play a "pure" form of the blues, but largely outside of mainstream notice. The structure of clubs, venues and festivals that had grown up in the early 1950s in Britain virtually disappeared in the 1970s.<ref>R. F.  Schwartz, ''How Britain Got the Blues: the Transmission and Reception of American Blues Style in the United Kingdom'' (Aldershot: Ashgate, 2007), p. 242.</ref>