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A chord, in music, is any harmonic set of three or more notes that is heard as if sounding simultaneously.〔Benward & Saker (2003). ''Music: In Theory and Practice, Vol. I'', p. 67&359. Seventh Edition. ISBN 978-0-07-294262-0."A ''chord'' is a harmonic unit with at least three different tones sounding simultaneously." "A combination of three or more pitches sounding at the same time."〕 These need not actually be played together: arpeggios and broken chords may, for many practical and theoretical purposes, constitute chords. Chords and sequences of chords are frequently used in modern Western, West African〔Mitchell, Barry (January 16, 2008). "(An explanation for the emergence of Jazz (1956) )", ''Theory of Music''.〕 and Oceanian〔Linkels, Ad, ''The Real Music of Paradise"'', In Broughton, Simon and Ellingham, Mark with McConnachie, James and Duane, Orla (Ed.), ''World Music, Vol. 2: Latin & North America, Caribbean, India, Asia and Pacific'', pp 218–229. Rough Guides Ltd, Penguin Books. ISBN 1-85828-636-0〕 music, whereas they are absent from the music of many other parts of the world.〔Malm, William P. (1996). ''Music Cultures of the Pacific, the Near East, and Asia''. p.15. ISBN 0-13-182387-6. Third edition: "Indeed this harmonic orientation is one of the major differences between Western and much non-Western music."〕 In tonal Western classical music, the most frequently encountered chords are triads, so called because they consist of three distinct notes: further notes may be added to give tetrads such as seventh chords and added tone chords, as well as extended chords and tone clusters. Triads commonly found in the Western classical tradition are major, minor, augmented and diminished chords. The descriptions ''major'', ''minor'', ''augmented'', and ''diminished'' are referred to collectively as chordal ''quality''. Chords are also commonly classified by their root note—for instance, a C major triad consists of the pitch classes C, E, and G. Chords may also be classified by inversion, the way in which their pitches are vertically arranged. An ordered series of chords is called a chord progression. Although any chord may in principle be followed by any other chord, certain patterns of chords have been accepted as establishing the key (tonic note) in common-practice harmony. To describe this, Western music theory has developed the practicing of numbering chords using Roman numerals〔Arnold Schoenberg, ''Structural Functions of Harmony'', Faber and Faber, 1983, p.1-2.〕 which represent the number of diatonic steps up from the tonic note of the scale. Common ways of notating or representing chords〔Benward & Saker (2003), p. 77.〕 in Western music other than conventional staff notation include Roman numerals, figured bass, macro symbols (sometimes used in modern musicology), and chord charts. Each of these systems is more likely to appear in certain contexts: figured bass notation was used prominently in notation of Baroque music, macro symbols are used in modern musicology, and chord charts are typically found in the lead sheets used in popular music and jazz. ==Definition and history== (詳細はMerriam-Webster's dictionary of English usage )'', p.243. ISBN 978-0-87779-132-4.〕 in the original sense of ''agreement'' and later, ''harmonious sound''.〔"(Chord )", ''Oxford Dictionaries''.〕 A sequence of chords is known as a chord progression or harmonic progression. These are frequently used in Western music.〔 A chord progression "aims for a definite goal" of establishing (or contradicting) a tonality founded on a key, root or tonic chord.〔 The study of harmony involves chords and chord progressions, and the principles of connection that govern them. Ottó Károlyi〔Károlyi, Ottó, ''Introducing Music'', p. 63. England: Penguin Books.〕 writes that, "Two or more notes sounded simultaneously are known as a chord," though, since instances of any given note in different octaves may be taken as the same note, it is more precise for the purposes of analysis to speak of distinct ''pitch classes''. Furthermore, as three notes are needed to define any common chord, three is often taken as the minimum number of notes that form a definite chord. Hence Andrew Surmani, for example, (2004, p. 72) states, "When three or more notes are sounded together, the combination is called a chord." George T. Jones (1994, p. 43) agrees: "Two tones sounding together are usually termed an ''interval'', while three or mores tones are called a ''chord''." According to Monath (1984, p. 37); "A chord is a combination of three or more tones sounded simultaneously," and the distances between the tones are called intervals. However sonorities of two pitches, or even single-note melodies, are commonly heard as ''implying'' chords. Since a chord may be understood as such even when all its notes are not simultaneously audible, there has been some academic discussion regarding the point at which a group of notes may be called a ''chord''. Jean-Jacques Nattiez (1990, p. 218) explains that, "We can encounter 'pure chords' in a musical work," such as in the ''Promenade'' of Modest Mussorgsky's ''Pictures at an Exhibition'' but, "Often, we must go from a textual given to a more ''abstract'' representation of the chords being used," as in Claude Debussy's ''Première Arabesque''. In the medieval era, early Christian hymns featured organum (which used the simultaneous perfect intervals of a fourth, a fifth, and an octave〔Duarter, John (2008). ''Melody & Harmony for Guitarists'', p.49. ISBN 978-0-7866-7688-0.〕), with chord progressions and harmony an incidental result of the emphasis on melodic lines during the medieval and then Renaissance (15-17th centuries).〔Benward & Saker (2003), p.185.〕〔Benward & Saker (2003), p.70.〕 The Baroque period, the 17th and 18th centuries, began to feature the major and minor scale based tonal system and harmony, including chord progressions and circle progressions.〔 It was in the Baroque period that the accompaniment of melodies with chords was developed, as in figured bass,〔 and the familiar cadences (perfect authentic, etc.).〔Benward & Saker (2003), p.100.〕 In the Renaissance, certain dissonant sonorities that suggest the dominant seventh occurred with frequency.〔Benward & Saker (2003), p.201.〕 In the Baroque period the dominant seventh proper was introduced, and was in constant use in the Classical and Romantic periods.〔 The leading-tone seventh appeared in the Baroque period and remains in use.〔Benward & Saker (2003), p.220.〕 Composers began to use nondominant seventh chords in the Baroque period. They became frequent in the Classical period, gave way to altered dominants in the Romantic period, and underwent a resurgence in the Post-Romantic and Impressionistic period.〔Benward & Saker (2003), p.231.〕 The Romantic period, the 19th century, featured increased chromaticism.〔 Composers began to use secondary dominants in the Baroque, and they became common in the Romantic period.〔Benward & Saker (2003), p.274.〕 Many contemporary popular Western genres continue to rely on simple diatonic harmony, though far from universally:〔Winston Harrison, ''The Rockmaster System: Relating Ongoing Chords to the Keyboard – Rock, Book 1'', Dellwin Publishing Co. 2005, p. 33 ()〕 notable exceptions include the music of film scores, which often use chromatic, atonal or post-tonal harmony, and modern jazz (especially circa 1960), in which chords may include up to seven notes (and occasionally more).〔Pachet, François, ''Surprising Harmonies'', International Journal on ComputingAnticipatory Systems, 1999. ()〕 Triads consist of three notes; the ''root'' or ''first'' note, the ''third'', and the ''fifth''.〔Pen, Ronald (1992). ''Introduction to Music'', p.81. McGraw-Hill, ISBN 0-07-038068-6. "In each case the note that forms the foundation pitch is called the ''root'', the middle tone of the chord is designated the ''third'' (because it is separated by the interval of a third from the root), and the top tone is referred to as the ''fifth'' (because it is a fifth away from the root)."〕 For example, the C major scale consists of the notes C D E F G A B: a triad can be constructed on any note of such a major scale, and all are minor or major except the triad on the seventh or leading-tone, which is a diminished chord. A triad formed using the note C itself consists of C (the root note), E (the third note of the scale) and G (the fifth note of the scale). The interval from C to E is of four semitones, a major third, and so this triad is called C Major. A triad formed upon the same scale but with D as the root note, D (root), F (third), A (fifth), on the other hand, has only three semitones between the root and third and is called D minor, a minor triad. 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 (music)」の詳細全文を読む スポンサード リンク
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