Although the koto has not undergone any essential changes since its introduction into Japan, several types can now be distinguished, depending on the musical genre or school in which they are used. The various types may be classified into four groups: gakusō, used in gagaku (court music); tsukushisō, the instruments of tsukushi-goto (the older tradition of koto music); zokusō, used in zokusō (the later tradition of koto music); and shinsō, the group of new koto types, many of which were invented by Miyagi Michio (1894–1956) and which are used in specially composed music. Shinsō include the jūshichigen (17-string bass koto) and the tangoto (a small koto, whose strings are tightened by pegs; the performer places it on a table and plays it sitting in a chair rather than kneeling on the floor).
The koto has a long (about 180–90 cm), slender (about 24 cm at the midpoint), rectangular body of kiri wood (Paulownia imperialis) with a slight convex longitudinal curve and larger lateral curve. There are 13 silk strings of equal length and thickness, stretched under equal tension over fixed bridges placed about 10 cm from the right end (as viewed by the player) and about 20 cm from the left end; nowadays stronger materials such as nylon and tetron are also used. The length of the vibrating part of the strings is determined by the placement of movable bridges (ji), each string having one bridge (for illustration of a koto bridge, see Bridge, fig.1e). The ji are made of wood or ivory (plastic is used on cheap modern instruments). Different placements of the ji produce different tunings. Depending on the player’s school, the strings are plucked with bamboo, bone or ivory plectra (tsume) of varying shape.
In all schools the player is behind the instrument, its right end slightly to his right. The player sits on the floor, cross-legged (in gagaku and Kyōgoku; see §(iv) below), kneeling (Ikuta and Yamada schools; see §(iii) below), or with one knee raised (traditionally in tsukushi-goto, although female players have now changed this ‘unfeminine’ position to a kneeling one). The Ikuta player kneels at an oblique angle, facing slightly to the left; in all other schools the player is positioned at a right angle to the instrument. The tsume are worn on thumb, index finger and middle finger of the right hand, and pluck towards the palmar side of the hand. The main playing digit is the thumb, which plucks the strings in a movement directed away from the player (fig.8). The main function of the left hand is to provide pitches not available on the open strings by pressing down on a string to the left of the movable bridge, raising the tension of the string and thereby the pitch (fig.9). The left hand is additionally used to produce ornamental pitch inflections. Direct plucking of the strings with the left hand, although used today, occurred only rarely before the late 19th century.
The tuning of the koto depends on the scale system of the musical genre or composition for which the instrument is used. All traditional tunings consist of five pitches to an octave, representing the five most important notes of the mode. Additional pitches may be obtained by left-hand pressure to the left of the movable bridges. The tunings of the koto in gagaku, tsukushi-goto and in Ryukyuan koto music approximate to the requirements of the Pythagorean system; in zokusō this is true for the first, fourth and fifth degrees; the second and sixth degrees are somewhat lower. The exact ‘lowness’ of these latter pitches is not standardized: the ‘minor 2nds’ in the tuning produced by the more traditional musician vary, averaging about 75 cents, whereas more modern musicians tend to equate this interval with the Western tempered semitone of 100 cents. The relation between scale and tuning in gagaku and tsukushi-goto is shown in ex.1; zokusō is represented by its typical scale (the in scale) and its three most common tunings (ex.2). The location of the first degree of the scale is shown in the tuning patterns, which shows that the zokusō tunings are transpositions of the same scale, not (as is often thought) different modes.
Japan, §II, 4: Instruments and instrumental genres, Koto.