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The short octave was a method of assigning notes to keys in early keyboard instruments (harpsichord, clavichord, organ), for the purpose of giving the instrument an extended range in the bass. A closely related system, the broken octave, is covered below. ==Short octave== In one variant of the short octave system, the lowest note on the keyboard was nominally E, but the pitch to which it was tuned was actually C. Nominal F was tuned to D, and nominal G was tuned to E. Thus, in playing the keys: E F G F G A B C the player would hear the musical scale of C major in the bass: C D E F G A B C The actual note assignments can be seen in the following diagram, which shows the lowest eight keys of an early keyboard: The rationale behind this system was that the low notes F and G are seldom needed in early music. Deep bass notes typically form the root of the chord, and F and G chords were seldom used at this time. In contrast, low C and D, both roots of very common chords, are sorely missed if a harpsichord with lowest key E is tuned to match the keyboard layout. When scholars specify the pitch range of instruments with this kind of short octave, they write "C/E", meaning that the lowest note is a C, played on a key that normally would sound E. A second type of short octave used the keys "B C E C D E F G" to play the G major scale "G A B C D E F G". Here, the exotic bass notes C and E are sacrificed to obtain the more essential A and B. The notation for the pitch range of such an instrument is "G/B". The following diagram illustrates this kind of short octave: In stringed instruments like the harpsichord, the short octave system created a defect: the strings which were tuned to mismatch their keyboard notes were in general too short to sound the reassigned note with good tone quality. To reach the lower pitch, the strings had to be thickened, or tuned too slack. During the 17th and 18th centuries, harpsichord builders gradually increased the size and bass range of their instruments to the point where every bass note could be properly played with its own key. Short octaves were very common in the early organ. Here, the practice would not have yielded poor tone quality (since the associated pipes would have to be built with the correct length in any event). Far more than on stringed instruments the financial savings would have been quite considerable, as the long pipes entailed quite an expense, even in materials alone. But as harmonic music developed more complexity in the late 17th and 18th centuries and the desire arose for completely chromatic bass octaves, short octaves ultimately came to be abandoned in organs as well. 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「Short octave」の詳細全文を読む スポンサード リンク
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