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In music, a rewrite rule is a recursive generative grammar, which creates a chord progression from another. Steedman (1984)〔Steedman M.J., "A Generative Grammar for Jazz Chord Sequences", ''Music Perception'' 2 (1) (1984) 52–77.〕 has proposed a set of recursive "rewrite rules" which generate all well-formed transformations of jazz, basic I–IV–I–V–I twelve-bar blues chord sequences, and, slightly modified, non-twelve-bar blues I–IV–V sequences ("rhythm changes"). The original progression may be notated as follows (typical 12-bar blues): 1 2 3 4 5 6 7 8 9 10 11 12 I/ I/ I/ I// IV/IV/ I/ I// V/ IV/ I/ I Where the numbers on the top line indicate each bar, one slash indicating a bar line and two indicating a phrase marking, and the Roman numerals indicating the chord function. Important transformations include *replacement or substitution of a chord by its dominant or subdominant: 1 2 3 4 5 6 7 8 9 10 11 12 I/IV/I/I7//IV/VII7/III7/VI7//II7/V7/I/I// *use of chromatic passing chords: ...7 8 9... ...III7/III7/II7... *and chord alterations such as minor chords, diminished sevenths, etc. Sequences by fourth, rather than fifth, include Jimi Hendrix's version of "Hey Joe" and Deep Purple's "Hush": 1 2 3 4 5 6 7 8 9 10 11 12 ♭VI, ♭III/♭VII, IV/I/I//♭VI, ♭III/♭VII, IV/I/I//♭VI, ♭III/♭VII, IV/I/I// These often result in Aeolian harmony and lack perfect cadences (V–I). Middleton (1990)〔Middleton, Richard (1990). ''Studying Popular Music'', p.198. ISBN 0-335-15275-9.〕 suggests that both modal and fourth-oriented structures, rather than being, "distortions or surface transformations of Schenker's favoured V-I kernel, are more likely branches of a deeper principle, that of tonic/not-tonic differentiation." For the ♭ notation, see Borrowed chord. ==Sources== 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「Chord rewrite rules」の詳細全文を読む スポンサード リンク
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