There are a number of different shamisen types, varying in size (though all are about 97 cm long), membrane thickness and material, bridge height and weight (fig.14a), string gauge and type of plectrum (fig.14b). A general distinction is made by the comparative thickness of the flat-topped fingerboard: thickest (futozao), medium-sized (chūzao) and thinnest (hosozao). The neck (sao) and pegbox (itokura) are now constructed in three sections so that the instrument can easily be taken apart and transported. The preferred woods for the neck and body are red sandalwood, mulberry and quince. The pegs (itomaki) are ivory, ebony or plastic; the strings are twisted silk, though the stronger synthetic material tetron is now often preferred to the fragile silk, especially for the treble string.
The upper bridge (kamikoma) of the neck is of special interest (fig.15): the two higher-pitched strings pass over a metal or ivory ridge at the pegbox, but the lowest string is set in a niche in the wooden edge of the box. Immediately below the upper bridge there is a slight cavity carved in the neck (the ‘sawari valley’): the bass string will buzz against the edge of this trough (the ‘sawari mountain’) when plucked or when resonating with notes a fifth or octave above it, producing a sound called sawari, which is of special value in shamisen music. Its invention in the 17th or 18th century may relate to the fact that early shamisen players previously used a larger lute, the biwa, which has a similar tonal characteristic, although it is differently constructed. In the 1890s a different method was devised, called azuma-zawari: a screw inserted from the back of the neck could be turned to adjust the degree of buzzing of the bass string against a tiny metal plate. Sawari is not found on the shamisen's Chinese and Okinawan ancestors. (Note that the term for the similar resonance on many Indian plucked instruments is jiwari.)
A tailpiece (neo) of silk rope holds the strings across the rectangular body, which is made of four convex pieces of wood covered at the front and rear by cat- or dogskin. Synthetic membranes are now common, partly for durability. Patterns (ayasugi) carved inside the body of expensive instruments affect the tone of the instrument, as does the quality of the skin. The skins are held by glue and shrinkage, without pegs or lashing. An extra semicircle of skin (bachikawa) is added at the top centre of the front head to protect it from the blows of the plectrum.
Good plectra (bachi) are of ivory or ivory-tipped wood except in certain chamber music (jiuta or sankyoku) and folk genres, for which tortoise-shell or buffalo-horn tips are used. Practice plectra may be made of plastic or wood. In some lighter forms of shamisen music, such as kouta, the side of the fingertip is used instead. For the style called shinnai-nagashi, one of two shamisenists plays a high obbligato using a capo (kase) and a tiny version of the standard plectrum. In most genres the wide edge and triangular tips of the plectrum are as thin as possible, but for gidayū they may be 2–4 mm thick. The sorts of difference shown in fig.15b affect timbre greatly.
The removable bridges (koma) are equally varied. They may be of ivory, tortoise-shell, buffalo-horn, plastic or wood. In jiuta the bridge may have small lead weights to help dampen the vibrations. A gidayū player may have a large graduated set of lead-weighted bridges to adjust to pitch, humidity etc; these can weigh over 20 g, while a nagauta bridge is under 4 g. For quiet practice a very wide ‘stealth bridge’ (shinobi-goma) reduces volume.
A small device (yubikake, yubisuri) of wool knitted over rubberized thread stretches weblike between the thumb and first finger of the left hand for ease of movement. Gidayū players often powder their left hand instead. Left-hand pizzicato (hajiki), slides (koki, suri) and ‘hammering-on’ (uchi) appear in most genres; right-hand up-plucks (sukui) and tremolo are also common. In some genres intended for large theatres or the open air (nagauta, gidayū, tsugaru-jamisen) the plectrum frequently strikes the membrane sharply, producing a percussive accompaniment to the plucked string; in other genres more suited to intimate settings (kouta, jiuta) this is minimized.
The basic pitch of a shamisen depends on the range of the singer, which may vary greatly. The three standard tunings shown in ex.7 may thus be several steps higher or lower. During long compositions the tunings may change frequently, and a few special tunings may appear. Most shamisen music is based on the yō-in scale system and its modes (see §I, 4).