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Musicians use various kinds of chord names and symbols in different contexts, to represent musical chords. In most genres of popular music, including jazz, pop, and rock, a chord name and the corresponding symbol are typically composed of one or more of the following parts: # The root note (e.g., C). # The chord quality (e.g., major, maj, or M). # The number of an interval (e.g., seventh, or 7), or less often its full name or symbol (e.g., major seventh, maj7, or M7). # The altered fifth (e.g., sharp five, or 5). # An additional interval number (e.g., add 13 or add13), in added tone chords. For instance, the name C augmented seventh, and the corresponding symbol Caug7, or C+7, are both composed of parts 1, 2, and 3. Except for the root, these parts do not refer to the notes that form the chord, but to the intervals they form with respect to the root. For instance, Caug7 indicates a chord formed by the notes C-E-G-B. The three parts of the symbol (C, aug, and 7) refer to the root C, the augmented (fifth) interval from C to G, and the (minor) seventh interval from C to B. A set of decoding rules is applied to deduce the missing information. Although they are used occasionally in classical music, these names and symbols are "universally used in jazz and popular music",〔 Benward & Saker (2003). ''Music: In Theory and Practice, Vol. I'', p. 78. Seventh Edition. ISBN 978-0-07-294262-0. 〕 usually inside lead sheets, fake books, and chord charts, to specify the harmony of compositions. Other notation systems for chords include:〔 Benward & Saker (2003). ''Music: In Theory and Practice, Vol. I'', p. 77. Seventh Edition. ISBN 978-0-07-294262-0. 〕 plain staff notation, used in classical music, Roman numerals, commonly used in harmonic analysis,〔Schoenberg, Arnold (1983). ''Structural Functions of Harmony'', p.1-2. Faber and Faber. 0393004783〕 figured bass, much used in the Baroque era, and macro symbols, sometimes used in modern musicology. == Advantages and limitations == Any chord can be denoted using staff notation, showing not only its harmonic characteristics but also its exact voicing. However, this notation, frequently used in classical music, may provide too much information, making improvisation difficult. In fact, although voicings can and do have a significant effect on the subjective musical qualities of a composition, generally these interpretations retain the central characteristics of the chord. This provides an opportunity for improvisation within a defined structure and is important to improvised music such as jazz. Other problems are that voicings for one instrument are not necessarily physically playable on another (for example, the thirteenth chord, played on piano with up to seven notes, is usually played on guitar as a 4- or 5-note voicing that is impossible to play on piano with one hand). As a result of these limitations, popular music and jazz use a shorthand that describes the harmonic characteristics of chords. This notation is more easily expressed in plain text and in handwriting than the relatively complicated process of writing chords on a staff. It is also faster to read. The first part of a symbol for a chord defines the root of the chord. The root of the chord is always played by one of the instruments in the ensemble (usually by a bass instrument). Failure to include the root means that the indicated chord is not played. By convention, the root alone indicates a simple major triad, i.e., the root, the major third, and the perfect fifth above the root. After this, various additional symbols are added to modify this chord. There is unfortunately no universal standard for these symbols. The most common ones are below. This notation does not easily provide for ways of describing all chords. Some chords can be very difficult to notate, and others that exist theoretically are rarely encountered. For example, there are 6 possible permutations of triads (chords with three notes) involving minor or major thirds and perfect, augmented, or diminished fifths. However, conventionally only four are used (major, minor, augmented and diminished). There is nothing to stop a composer using the other two, but the question of what to call them is interesting. A minor third with an augmented fifth might be denoted, for example, by Am+, which would strike most musicians as odd. In fact, this turns out to be the same as F/A (see slash chords below). A major third with a diminished fifth might be shown as A(5). Usually, when composers require a chord that is not easily described using this notation, they indicate the required chord in a footnote or in the header of the music. 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 names and symbols (popular music)」の詳細全文を読む スポンサード リンク
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