This ancient instrument was said to have been brought to Japan from China in the 9th century. It is considered a distant relative of the ancient Chinese instrument- the qin, which dates back to the 5th century.
In the Japanese literature, the earliest mention of this instrument was written in an ancient handsroll in the Genji Monogatari or The Tale of Genji 12thC (translated in English as follows):
“Is my lord aware
Of an agitated heart
Unsteady as the rope
Slackened when our vessel halts
Charmed by the sound of a koto?” -Gosheki lady
The refined music of the koto is well known to several foreigners because it has become familiar outside Japan thanks to concerts, records, and CD’s. Whether performed as a solo instrument or in an ensemble, having a vocal part or without one, for several centuries the koto has been among the most popular traditional music instruments of Japan.
The modern-day koto is a long (nearly 1.8 meters), wooden instrument with 13 strings, traditionally silk but now, also nylon is used. Bridges (known as ji) bear the strings above the surface of the instrument, one bridge for every string. These bridges can be moved so that the player can adjust them at various places across the string, depending on the needed tuning.
image via Wikipedia
Similar to the prototype of the shakuhachi, the ancestor of the koto came to Japan from China in the early centuries of cultural interchange, then the instrument was slowly adapted to its current form. After many centuries of use by an elite few, in the Tokugawa period the koto slowly spread in popularity to other segments of Japanese society. At this time, changes in learning and in the koto repertoire induced numerous men and women to learn it (Malm 1959:169). Growing numbers included merchants, the class that formally held the bottom status but which was advancing quickly in riches and influence. Near the beginning of the Meiji period in 1868, the koto could be discovered in numerous private homes and in teahouses and theaters, and skilled koto operation had become a mark of good upbringing for young women. A lot of of the sokyoku (or koto music) pieces played today were composed in the Tokugawa period, when fresh schools and styles of performing rose up. During this time the koto was involved in ensembles with the shamisen, and later, the kokyu or shakuhachi, combinations that contributed a significant form of chamber music into Japanese life.
The Kumiuta and Danmono Traditions of Japanese Koto Music by Willem Adriaansz
Selections from The tale of Genji and The tale of the Heike by Helen Craig McCullough and Murasaki ShikibuJazz Journeys to Japan: The Heart Within By William Minor