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The 12-bar blues or ''blues changes'' is one of the most prominent chord progressions in popular music. The blues progression has a distinctive form in lyrics, phrase, chord structure, and duration. In its basic form, it is predominantly based on the I-IV-V chords of a key. The blues can be played in any key. Mastery of the blues and rhythm changes are "critical elements for building a jazz repertoire".〔Thomas 2002, p. 85.〕 ==Structure== In the key of C, one extremely common blues progression (B from above) is as follows.〔Benward & Saker 2003, p. 186.〕 : ''Popular music symbols'' C C C C or C7 C7 C7 C7 F F C C or F7 F7 C7 C7 G F C C or G7 F7 C7 C7 Chords may be also represented with a few different notation systems. A basic example of the progression would look like this, using T to indicate the tonic, S for the subdominant, and D for the dominant, and representing one chord. In Roman numeral analysis the tonic is called the I, the sub-dominant the IV, and the dominant the V. (These three chords are the basis of thousands more pop songs which thus often have a ''blues'' sound even without using the classical 12-bar form.) Using said notations, the chord progression outlined above can be represented as follows.〔Kernfeld 2007〕 The first line takes four bars, as do the remaining two lines, for a total of twelve bars. However, the vocal or lead phrases, though they often come in threes, do not coincide with the above three lines or sections. This overlap between the grouping of the accompaniment and the vocal is part of what creates interest in the twelve bar blues. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Twelve-bar blues」の詳細全文を読む スポンサード リンク
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