The 17-string koto (十七絃 or 十七弦 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.
Though Miyagi also invented an 80-string koto and a short koto, these did not catch on and spread as the jūshichi-gen did. It is still used today in various forms of traditional music; some of its more prominent exponents include Kazue Sawai, Shoko Hikage, and Miya Masaoka. The members of the Japanese band Rin' are among those who use the instrument in modern popular music.