The Koto is a Japanese zither, about two metres in length. It has about a dozen silk strings stretched across a wooden board. It has a moveable bridge, for raising the pitch of a note. Strings are plucked with the fingers, or the player may wear plectrums attached to their finger-nails. 

The koto is usually tuned to the pentatonic scale, which has only the 5 notes corresponding to our western scale degrees of 1, 2, 3, 5,  and 6.