The most common blues form is the so called twelve-bar blues, which spread during the 1920s and 30s. Sometimes a blues also has 8, 16 or another number of bars. A twelve-bar blues has a typical order of three different chords, and its form reflects a call and response scheme (4 bars call - 4 bars call - 4 bars response).
It is a mixture of a classical chord scheme, but with non-traditional, extended chords, and African melodics (pentatonic scale with microtone intonations). These vocal microtone intonations can be reproduced by guitar string bendings. Blues lyrics often deal with lamentation over an unhappy love affair, or unhappy life circumstances.
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