Writing KOTO music

By moving the bridges on the koto, it is possible to tune each string to either of its extremes. The standard rage of the 13-string koto can be from a low C to double high C; for the 17-string koto, from double low C to middle G; allowing flexibility within this range, including mircrotones.

The 13-string koto has numerous traditional tunings. Hirajoshi, a minor pentatonic scale, is the most basic of all traditional tunings. Oshide, a pressing technique by the left hand, can raise each note by a half step, a whole step, and anything in between.

Aside from the traditional tunings, it is possible to use tunings based on diatonic scales, 12-tone rows, as well as modes. If a composition calls for a tuning change during the piece, the koto performer can move the bridge/s.

The basic technique used to produce a sound on the koto is to pluck the string with the plectrum on the thumb of the right hand. The index finger and middle finger pluck in the opposite direction of the thumb. The remaining two fingers are used for pizzicato. 

Kakite: plucking of two strings with the middle finger.

Warizume: adjacent string plucking with repetition by the index and middle fingers.

Awasezume: simultaneous plucking of two strings with the thumb and middle finger.

Sukuizume: uses the back of the plectrum on the thumb in a scooping motion.

Oshiawase: pressing and plucking together.

Uraren: combination with tremolo, a downward glissando at the back of the plectrums on the index and middle fingers, and the last two or three notes by the plectrum on the thumb.

Chirashizume or waren: makes a quick swipe on a string from right to left with the side of the plectrum.

Uchizume: strike by the face of plectrum near the tsume (plectrum) ring.

Hikiren: the upward glissando.

Nagashizume: the downward glissando. 

Until the early 20th century, left-hand technique on the koto was limited to oshide (pressing), hikiiro (pulling), yuriiro (vibrato) and others that changed the timbre and pitch by using the area on the left side of the bridges. With the influx of Western music into Japan, koto composers began creating new left-hand techniques. With the influence of contemporary music after the 1960s, numerous possibilities have been explored.

On the koto, pizzicato is used to refer to pitches produced with the tips of the fingers, in contrast to the normal method of plucking with the plectrum. When producing pizzicato with the left hand, it is possible to use all the fingers. The fourth finger of the right hand can be used for pizzicato as well.

When muting the koto, one of the fingers of the left hand is placed on a string where it passes over the top of the bridge.

Harmonics are produced by placing the tip of a finger or the side of the palm of the left hand on the middle point of the string, and plucks with either the right hand or an available finger on the left hand.

It is also possible to create a distinctive effect by hitting the strings or the body with a hand, plectrum or a stick. Other experimental techniques include the use of a bow, the muting by applying wooden chopsticks, or the use of a hard object as a sliding bar, such as a glass.

In traditional koto performance, the player plucks the strings in the same fixed position near the ryukaku (the fixed bridge on the right of the performer). The different timbres can be obtained according to the distance/position from the ryukaku.

The 17-string bass koto was originally created to support the lower harmony in an ensemble. It has since been developed as a solo musical instrument. 

The strings and bridges are thicker than the 13-string koto, producing a deeper sound, and longer resonances.