Writings combining elements of gagaku music theory and the Chinese theories of yin-yang and the five elements dealt with a great variety of non-musical phenomena: the seasons, colors, directions, and so on. Perhaps the grandest expression of this imaginative way of thinking can be seen in a rather unusual work of music theory, Kangen ongi (‘Meaning of the Tones of Pipes and Strings’).

The five tones and their associations

Many works were written on music during the Heian period (9th to 12th centuries), when gagaku was at its most popular. Most of them were of practical content, written by the members of musician families for their own use, but also included accounts of the relationship between the five modes and/or tones and other natural and cultural phenomena, such as the five elements, the seasons, the directions, and the nation.

Kangen ongi (‘Meaning of the Tones of Pipes and Strings’) is thought to have been written in 1185 by one Ryōgon, a retired musician living in the ‘northern mountains’ area of the capital, Kyoto. It differs from other works on music of the period in that, while lacking in practical content, it concentrates instead on what might be called a metaphysical cosmology centered on music. We know little of Ryōgon other than that he was once a priest of the Shitennō-ji lineage.

This work quotes many works of Chinese and Japanese origin while explaining the meanings and associations of seven tones, which are grouped into five basic tones—namely ichikotsu(D), hyōjō (E), sōjō (G), ōshiki (A), and banshiki (B)—and two auxiliary tones—shimomu (F#) and kamimu (C#). Its explanations are largely unrelated to practical matters and difficult to follow; not limited to pitch, they deal with such things as five of the human organs (heart, liver, etc.) and the five senses (taste, smell, etc.). It is valuable, however, in that it gives us a glimpse of the philosophical background of gagaku.