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A chord progression or harmonic progression is a series of musical chords, or chord changes that "aims for a definite goal" of establishing (or contradicting) a tonality founded on a key, root or tonic chord〔Arnold Schoenberg, ''Structural Functions of Harmony'', Faber and Faber, 1983, p.1-2.〕 and that is based upon a succession of root relationships.〔Benward & Saker (2003). ''Music: In Theory and Practice, Vol. I'', p.178. Seventh Edition. ISBN 978-0-07-294262-0.〕 Chords and chord theory are generally known as harmony. A chord progression can be thought of as a ''harmonic'' simultaneity succession: it offers an ongoing shift of level that is essential to many musical traditions. A change of chord, or "chord change", generally occurs on an accented beat, so that chord progressions may contribute significantly to the rhythm, meter and musical form of a piece, delineating bars, phrases and sections.〔Stewart MacPherson, ''Musical Form'', Chapter 1, Joseph Williams, London, 1930.〕 This is known as harmonic rhythm. ==Basics== A chord may be built upon any note of a musical scale, therefore a seven-note scale allows seven basic chords, each degree of the scale becoming the root of its own chord.〔George Whitefield Chadwick, ''Harmony: A Course of Study'', 72nd Ed. B.F.Wood Music Co., 1922, Introduction p. xv〕 A chord built upon the note A is an A chord of some type (major/minor/diminished, etc.) The harmonic ''function'' of any particular chord depends on the context of the particular chord progression in which it is found.〔 (''See'' Diatonic function) The diatonic harmonization of any major scale results in three major triads. They are based on the first, fourth, and fifth scale degrees (the tonic, subdominant and dominant〔Chadwick, 1922, p.1〕 – ''see three-chord song''). These three triads include, and therefore can harmonize, every note of that scale. The same scale also provides three relative minor chords, one related to each of the three major chords. These are based upon the sixth, second and third degrees of the major scale and stand in the same relationship to one another as do the three majors, so that they may be viewed as the first, fourth and fifth degrees of the relative minor key. Separate from these six common chords there is one degree of the scale, the seventh, that results in a diminished chord.〔C.H. Kitson, ''Elementary Harmony, Part One'', O.U.P., 1920, Chapters 3-4.〕 In addition, extra notes may be added to any chord. If these notes are also selected from the original scale the harmony remains diatonic. If new chromatic intervals are introduced then a change of scale or modulation occurs, which may bring the sense of a change of tonal center. This in turn may lead to a resolution back to the original key, so that the entire sequence of chords helps create an extended musical form. Although all this allows for a large number of possible progressions (depending upon the length of the progression), in practice, progressions are often limited to a few bars' length and certain progressions are favored above others: there is a certain amount of fashion in this and a chord progression may even define an entire genre. In western classical notation, chords built on the scale are numbered with Roman numerals. A D chord will be figured I in the key of D, for example, but IV in the key of A. Minor chords are signified by lower case Roman, so that D minor in the key of C would be written ii. Other forms of chord notation have been devised, from figured bass to the chord chart. These usually allow or even require a certain amount of improvisation. 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 progression」の詳細全文を読む スポンサード リンク
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