The scale with the widest distribution throughout Ryūkyū is a variant of the ritsu scale (ex.21c). This appears especially in kamiuta and folk songs in the Yaeyama, Miyako and northern Okinawan regions. The scale more generally associated with the music of Ryūkyū, however, is the Okinawa scale and its variants (ex.21a, b, d). This scale is associated in particular with sanshin music, although it is not present in the Amami region, except in the southernmost islands where Okinawan music has entered.
There are four main features of the use of the Okinawa scale in classical music. First, a core pentatonic or hexatonic scale is present within the framework of an approximate diatonic series. Second, there may be either one or two tonal centres; when there are two, they fall on the first and fourth degrees (ex.21a, d). Third, the seventh degree in ex.21a and the fourth degree in ex.21b are approximately a quarter-tone flat and are inherently unstable. Finally, ex.21d is the only scale in which all pitches fall within a strict diatonic series. A variant of this scale in which only the first degree constitutes a nuclear pitch is the scale most commonly employed in modern folk music.
The formal structure of the music is determined largely by that of the song texts; there is no direct expressive linkage between texts and music. Ryūka texts generally appear in anthologies classified according to the piece (fushi) to which they are sung. In many cases, any of several dozen texts may be sung to a particular piece, and the music in no way represents a ‘setting’ of a specific verse. In the case of extended texts, the form in both classical and folk music is generally strophic, as in the kuduchi genre. Various forms are used in the case of the ryūka texts to which the majority of songs are sung. Ha-bushi pieces in their simplest form have an AA form corresponding to the 8–8 and 8–6 lines of the text (e.g. Guin-bushi). In this case it is customary for two syllables in the last line to be repeated. AA' form involves compression of the musical material to accommodate the six-syllable length of the last line (e.g. Chūjun-bushi). Other ha-bushi pieces have a more complex structure, in which the music of the last two lines is repeated after an episode (e.g. Kajadifū-bushi, Hanafū-bushi). Others have no repetition of formal units (e.g. Chin-bushi) or may incorporate hayashi-kotaba, meaningless phrases or syllables unconnected with the meaning of the main text (e.g. Chirurin-bushi). The formal structure of nkashi-bushi is most commonly AABC (with B constituting an instrumental interlude), in which the music corresponding to the first line of the ryūka verse is repeated for the second line (e.g. Akatsichi-bushi). Many pieces, however, have formal structures of considerably greater complexity.
Every piece in the sanshin repertory incorporates a short instrumental passage (utamuchi) performed several times at the beginning and at the end of a song. In dance pieces this is repeated continuously as the dancers enter and leave the stage.