The Electric blues reference article from the English Wikipedia on 24-Apr-2004
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Electric blues

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The electric blues is a type of blues music distinguished simply by the amplification of the guitar, or, more rarely, the bass or harmonica. Electric blues can be any other kind as well, most commonly Chicago, Texas or Memphis blues.

The electric blues first emerged as a full-fledged genre in the mid-1940s. The original artists performing this style became heroes to a great many British youth, who began imitating their styles (see British blues). After a period of slavish imitation, British musicians began inventing their own style, which became wildly popular during the 1960s as part of the British Invasion.