17-string koto
The 17-string koto (Japanese: 十七絃 or 十七弦, Hepburn: jūshichi-gen; "seventeen strings") is a variant of the koto with 17 strings instead of the typical 13. The instrument is also known as jūshichi-gensō (十七絃箏), "17 stringed koto", or "bass koto" (although koto with a greater number of strings also exist).