How did koto notation change during the Tokugawa period?

During the Tokugawa period (1603–1867), koto notation evolved from simple mnemonic patterns toward more visually precise systems. Early printed collections from the 17th century, such as the Shichiku shōshinshū (1664), primarily featured song texts accompanied by string numbers, names of stereotyped patterns, or mnemonics to aid rote learning.1

In the late 18th century, notation became more sophisticated to better represent musical structure. The Sōkyoku taisho (1779) introduced the use of various-sized dots to indicate rhythm. By the early 19th century, this progressed to a system where string numbers were placed within columns of squares to represent rhythmic timing. These developments eventually integrated with Western concepts, such as bar lines, leading to the distinct but balanced notation systems used by the Ikuta and Yamada schools today.1