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In modern musical notation and tuning, an enharmonic equivalent is a note, interval, or key signature that is equivalent to some other note, interval, or key signature but "spelled", or named differently. Thus, the enharmonic spelling of a written note, interval, or chord is an alternative way to write that note, interval, or chord. For example, in twelve-tone equal temperament (the currently predominant system of musical tuning in Western music), the notes C and D are ''enharmonic'' (or ''enharmonically equivalent'') notes. Namely, they are the same key on a keyboard, and thus they are identical in pitch, although they have different names and different roles in harmony and chord progressions. In other words, if two notes have the same pitch but are represented by different letter names and accidentals, they are enharmonic.〔Benward & Saker (2003). ''Music in Theory and Practice, Vol. I'', p.7 & 360. ISBN 978-0-07-294262-0.〕 "''Enharmonic intervals'' are intervals with the same sound that are spelled differently...(), of course, from enharmonic tones."〔Benward & Saker (2003), p.54.〕 Prior to this modern meaning, "enharmonic" referred to notes that were very close in pitch—closer than the smallest step of a diatonic scale—but not identical in pitch, such as F and a flattened note such as G.〔Louis Charles Elson (1905) Elson's Music Dictionary, p.100. O. Ditson Company. "The relation existing between two chromatics, when, by the elevation of one and depression of the other, they are united into one".〕 as in enharmonic scale. "Enharmonic equivalence is peculiar to post-tonal theory."〔Don Michael Randel, ed. (2003). "Set theory", ''The Harvard Dictionary of Music'', p.776. Harvard. ISBN 9780674011632.〕 "Much music since at least the 18th century, however, exploits enharmonic equivalence for purposes of modulation and this requires that enharmonic equivalents in fact be equivalent."〔Don Michael Randel, "Enharmonic", ''The Harvard Dictionary of Music'', fourth edition (Cambridge: Belknap Press of Harvard University Press, 2003), p.295. ISBN 978-0-674-01163-2.〕 Some key signatures have an enharmonic equivalent that represents a scale identical in sound but spelled differently. The number of sharps and flats of two enharmonically equivalent keys sum to twelve. For example, the key of B major, with 5 sharps, is enharmonically equivalent to the key of C-flat major with 7 flats, and 5 (sharps) + 7 (flats) = 12. Keys past 7 sharps or flats exist only theoretically and not in practice. The enharmonic keys are six pairs, three major and three minor: B major/C-flat major, G-sharp minor/A-flat minor, F-sharp major/G-flat major, D-sharp minor/E-flat minor, C-sharp major/D-flat major and A-sharp minor/B-flat minor. There are practically no works composed in keys that require double sharping or double flatting ''in the key signature''. In practice, musicians learn and practice 15 major and 15 minor keys, three more than 12 due to the enharmonic spellings. For example the intervals of a minor sixth on C, on B, and an augmented fifth on C are all enharmonic intervals . The most common enharmonic intervals are the augmented fourth and diminished fifth, or tritone, for example C-F = C-G.〔 Enharmonic equivalence is not to be confused with octave equivalence, nor are enharmonic intervals to be confused with inverted or compound intervals. ==Tuning enharmonics== In principle, the modern musical use of the word ''enharmonic'' to mean identical tones is correct only in equal temperament, where the octave is divided into 12 equal semitones. In other tuning systems, however, enharmonic associations can be perceived by listeners and exploited by composers.〔Rushton, Julian (2001). "Enharmonic", ''The New Grove Dictionary of Music and Musicians''. Second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers. ISBN 0-19-517067-9.〕 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「enharmonic」の詳細全文を読む スポンサード リンク
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