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In music, an accidental is a note of a pitch (or pitch class) that is not a member of the scale or mode indicated by the most recently applied key signature. In musical notation, the sharp (), flat (), and natural () symbols, among others, mark such notes—and those symbols are also called accidentals. In the measure (bar) where it appears, an accidental sign raises or lowers the immediately following note (and any repetition of it in the bar) from its normal pitch, overriding sharps or flats (or their absence) in the key signature. A note is usually raised or lowered by a semitone, although microtonal music may use "fractional" accidental signs. One occasionally sees double sharps or flats, which raise or lower the indicated note by a whole tone. Accidentals apply within the measure and octave in which they appear, unless canceled by another accidental sign, or tied into a following measure. If a note has an accidental and the note is repeated in a different octave within the same measure, the accidental does not apply to the same note of the different octave. The modern accidental signs derive from the round and square small letter ''b'' used in Gregorian chant manuscripts to signify the two pitches of B, the only note that could be altered. The round ''b'' became the flat sign, while the square ''b'' diverged into the sharp and natural signs. Sometimes the black keys on a musical keyboard are called accidentals or ''sharps'', and the white keys are called ''naturals''.〔Palmieri, Robert, and Margaret W. Palmieri. "Ebonies", (''Piano: An Encyclopedia'' ), p.118. New York: Routledge, 2003. ISBN 0-415-93796-5. "The ebonies are the black keys of a piano, called variously sharps or accidentals, …" "The ivories are the white keys of the piano (also called naturals), ..."〕 ==Standard use of accidentals== In most cases, a sharp raises the pitch of a note one semitone while a flat lowers it a semitone. A natural is used to cancel the effect of a flat or sharp. This system of accidentals operates in conjunction with the key signature, whose effect continues throughout an entire piece, unless canceled by another key signature. An accidental can also be used to cancel a previous accidental or reinstate the flats or sharps of the key signature. Accidentals apply to subsequent notes on the same staff position for the remainder of the measure in which they occur, unless explicitly changed by another accidental, as shown at right. Notes on other staff positions. Once a barline is passed, the effect of the accidental ends, except when a note affected by an accidental is tied to the same note across a barline. Subsequent notes at the same staff position in the second or later bars are not affected by the accidental carried through with the tied note. Though this convention is still in use particularly in tonal music, it may be cumbersome in music that features frequent accidentals, as is often the case in non-tonal music. As a result, an alternative system of note-for-note accidentals has been adopted, with the aim of reducing the number of accidentals required to notate a bar. The system is as follows:〔Stone, Kurt. ''Music Notation in the Twentieth Century: A Practical Guidebook'', . New York: W. W. Norton & Co., 1980.〕 # An accidental carries through the bar affecting both the note it immediately precedes and any following notes on the same line or space in the measure. # Accidentals do not affect the same note of a different octave, unless indicated by a key signature.〔Manoff, T: "The Music Kit Workbook", fourth edition (New York: W. W. Norton & Company, 2001): p. 47; Anthony Pryer, "Accidental", ''The Oxford Companion to Music'', edited by Alison Latham (Oxford and New York: Oxford University Press, 2002). ISBN 9780198662129; Gardner Read, ''Music Notation: A Manual of Modern Practice'' (Boston: Allyn & Bacon, 1969): 126.〕 # Accidentals are not repeated on tied notes unless the tie goes from line to line or page to page. # Accidentals are not repeated for repeated notes unless one or more different pitches (or rests) intervene. # If a sharp or flat pitch is followed directly by its natural form, a natural is used. # Cautionary accidentals or naturals (in parentheses) may be used to clarify ambiguities, but should be kept to a minimum. Because seven of the twelve notes of the chromatic equal-tempered scale are naturals (the ''white notes'', A; B; C; D; E; F; and G on a piano keyboard) this system can significantly reduce the number of naturals required in a notated passage. Occasionally an accidental may change the note by more than a semitone: for example, if a G is followed in the same measure by a G, the flat sign on the latter note means it is two semitones lower than if no accidental were present. Thus, the effect of the accidental must be understood in relation to the "natural" meaning of the note's staff position. For the sake of clarity, some composers put a natural in front of the accidental. Thus, if in this example the composer wanted the note a semitone lower than G-natural, he might put first a sign to cancel the previous G, then the . However, in most contexts, an F could be used instead. Double accidentals raise or lower the pitch of a note by two semitones,〔Bruce Benward & Marilyn Nadine Saker, ''Music in Theory and Practice'', seventh edition (Boston: McGraw-Hill, 2003): vol 1, p. 6. "''Double Sharp'' ()—raises the pitch two half steps. ''Double Flat'' ()—lowers the pitch two half steps."〕 an innovation developed as early as 1615. This applies to the written note, ignoring key signature. An F with a double sharp applied raises it a whole step so it is enharmonically equivalent to a G. Usage varies on how to notate the situation in which a note with a double sharp is followed in the same measure by a note with a single sharp: some publications simply use the single accidental for the latter note, whereas others use a combination of a natural and a sharp, with the natural being understood to apply to only the second sharp. The double accidental with respect to a specific key signature raises or lowers the notes containing a sharp or flat by a semitone. For example, when in the key of C minor or E major, F, C, G, and D contain a sharp. Adding a double accidental (double sharp) to F in this case only raisees F by one further semitone, creating G natural. Conversely, adding a double sharp to any other note not sharped or flatted in the key signature raises the note by two semitones with respect to the chromatic scale. For example, in the aforementioned key signature, any note that is not F, C, G, and D is raised by two semitones instead of one, so an A double sharp raises the note A natural to the enharmonic equivalent of B natural. 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「Accidental (music)」の詳細全文を読む スポンサード リンク
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