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The 17-string koto (Japanese: 十七絃 or 十七弦, Hepburn: jūshichi-gen, lit. "seventeen strings") is a traditional Japanese musical instrument, a zither with seventeen strings. It is a variant of the koto, which traditionally has thirteen strings.
The instrument is also known as jūshichi-gensō (十七絃箏), "seventeen-stringed koto", or "bass koto" (although kotos with a greater number of strings also exist). The jūshichi-gen was invented in 1921 by Michio Miyagi, a musician who felt that the standard koto lacked the range he sought. His seventeen-stringed creation, sometimes described as a "bass koto", has a deeper sound and requires specialized plectra (picks worn attached to the player's fingers with which the strings are plucked). Though his original jūshichi-gen was considerably larger than a normal koto, seventeen-stringed koto of a normal koto size are more common today; these presumably do not have as deep a sound.
The bass koto is similarly made from the Paulownia tomentosa (kiri) wood but the thickness of the wood so taken is approximately twice than that of a single koto. The wood is dried and treated by the traditional method until it gets good for construction. The strings used are made up of silk threads which are yellow in colour. They give a deep sound. These strings are tied from one end up to another one and a platform is created made of ivory. Then, the strings are tied over small cylindrical holders with holes and tied very tightly to the downside. The bridges (jī) are also even bold than the common bridges used in koto. The plectra used are made from special ivory so that plucking can be done easily. During playing there is a danger that the bridges can fall from their place, but the strings are tied so that the bridges cannot fall off but can be moved. Some of the players also used to colour some specific bridges so that while playing, they would not fall.
Advanced techniques of playing
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Players also invented new techniques for playing a Bass-Koto. It uses more use of the left hand as it produces a deep sound which lasts for a longer time. This helps to create more pitches at one string. The strings are also plucked over the cylindrical holder to create a sudden shrill. The area of koto towards the left side is also plucked by left hand. This creates a very good and humbling tune.