A nice quote from Kōdō Sawaki. Taken from the Dogen Institute blog: https://dogeninstitute.wordpress.com/2014/11/18/sawaki-on-the-poetry-of-shodoka/.
The first Zen poem that appeared in China is the Shinjinmei of the third patriarch. The second text in verse is the Shōdōka. The poem is in Chinese, but in order to render it accessible to the Japanese reader, I have introduced kana and restructured the phrases in the Japanese order. Nevertheless, I advise the reading of it in Chinese to better appreciate its extraordinary flavor.
We know the quality of the Indian dharani, of the Japanese haiku and waka, but the resonance of Chinese poetry is completely exceptional. Zen was introduced into China at a time when the writings of Lao-tzu were in vogue and Taoism had exercised a profound influence. I am not an historian, and I cannot say if it’s due to the Zen or to the Chinese, but the poetry of this epoch sounds clear to the ear and crackles on the tongue. The highly subtle verses are sharpened like a razor. For whatever reason, a new literary genre with unique resonances was brought to life.
The verses of the Shōdōka sound clear and strong when read aloud. The rhythm of the verses and the modulation of the sounds render their recitation easy. In addition to the Shōdōka, numerous Zen songs belong to the same genre, such as the Shinjinmei, Sandōkai. and Hōkyō Zanmai, or also the poems to recite, Senshi and Shinpō, as well as the poem Sōan by Sekitō Daishi.
These long poems antedate the Hekigan. They were put to music and gave birth to the music of ceremony. The Chinese poems are rhythmic and melodious; their impact is still greater when one chants them. It is not a didactic poetry aiming at touching the intellect. Rather, it is like playing an instrument or listening to music. One experiences a religious feeling simply by reciting them.