Koto, musical instrument, a Japanese long zither, with a long, convex upper board and a movable ivory bridge for each of its 13 silk strings. The body of the koto consists of a long, rectangular box, made of paulownia wood, about 180 cm (about 6 ft) in length and about 24 cm (about 9 in) in width. The instrument is strung lengthwise, and the strings are tuned by moving the bridges. The koto player sits either on the floor or in a chair behind the instrument, which rests on the floor or on a stand. The koto is played using plectrums, or picks, of bamboo, bone, ivory, or plastic attached to the thumb, index finger, and middle finger of the player's right hand. The player plucks a string to the right side of its bridge while the fingers of the left hand depress the plucked string on the opposite side of the bridge to create an upward or downward sliding after each tone. The flexible tuning of the instrument accommodates traditional pentatonic scales as well as other scales used in contemporary or European-influenced pieces. The harplike sound of the koto renders the instrument suitable for use as a solo instrument or in modern and traditional ensembles. In modern instruments, nylon strings are sometimes used instead of silk, and the bridges are sometimes made of plastic instead of ivory.