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Binary form is a musical form in two related sections, both of which are usually repeated. Binary is also a structure used to choreograph dance. In music this is usually performed as A-A-B-B Binary form was popular during the Baroque period, often used to structure movements of keyboard sonatas. It was also used for short, one-movement works. Around the middle of the 18th century, the form largely fell from use as the principal design of entire movements as sonata form and organic development gained prominence. When it is found in later works, it usually takes the form of the theme in a set of variations, or the Minuet, Scherzo, or Trio sections of a Minuet and Trio or Scherzo and Trio movement in a sonata, symphony, etc. Many larger forms incorporate binary structures, and many more complicated forms (such as sonata forms) share certain characteristics with binary form. ==Structure== Most strictly, a piece in binary form is characterized by two complementary, related sections of roughly equal duration, which come up frequently. The first section will start in a certain key, and will usually modulate to a related key: *compositions in major keys will typically modulate to the dominant, the fifth scale degree above the tonic *compositions in minor keys will typically modulate to the relative major, the major key centered on the third scale degree above the tonic; alternatively the first section could close in the dominant minor, or with an imperfect cadence in the original key. The second section of the piece begins in the newly established key, where it remains for an indefinite period of time. After some harmonic activity, the piece will eventually modulate back to its original key before ending. More often than not, especially in 18th-century compositions, the A and B sections are separated by double bars with repeat signs, meaning both sections were to be repeated.〔Bartlette, Christopher, and Steven G. Laitz (2010). Graduate Review of Tonal Theory. New York: Oxford University Press, pg 156. ISBN 978-0-19-537698-2〕 Binary form is usually characterised as having the form ''AB'', though since both sections repeat, a more accurate description would be ''AABB''. Others, however, prefer to use the label ''AA′''. This second designation points to the fact that there is no great change in character between the two sections. The rhythms and melodic material used will generally be closely related in each section, and if the piece is written for a musical ensemble, the instrumentation will generally be the same. This is in contrast to the use of verse-chorus form in popular music—the contrast between the two sections is primarily one of the keys used. 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「Binary form」の詳細全文を読む スポンサード リンク
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