Another excerpt from my upcoming book, "Tea: A Nerd's Eye View:"
You may see Tie Guan Yin tea advertised as having a “Yin Yun” or “Yin Rhyme” aftertaste, and Wuyi rock teas as having a quality called “Yan Yun.” “Yun” in this context means “rhyme.”
What would a rhyme have to do with a tea’s aftertaste?
With respect to rock teas, “Yan” can mean “rock,” but it also refers to the “male” principle—saying that rock tea has “Yan” is really a pun.
To understand the many layers of this play on words, it is important to know that Chinese singing and by extension Chinese poetry have a Yan (masculine) and Yin (feminine) rhyme system.
This system differs from the rhyme systems in English, though we have some of the same underlying concepts of masculine and feminine. In English we speak of masculine rhymes as consisting of one syllable, and feminine rhymes as consisting of two or more syllables. The English masculine rhyme can be abrupt and in your face, while the feminine rhyme is more supple and musical. The Chinese masculine and feminine rhymes have similar qualities.
As Ray Wen Wei states:
“Shih is a modem style of poetry (''jin ti shi") matured during the early Tang [618-690 CE]. It constrains a poem to eight lines of five or seven syllables each. With a single rhyme [system] running through it, the poem is divided into four pairs, namely "starting," "extending," "turning," and "completing," respectively. These appear in the western classical sonata form of music in the same order, as the "theme," "development," "transition," and "recapitulation." The rhyme used throughout the poem is chosen from one of two divisions of the vowel sounds. In general, these are divided as either long, bright sounds (called "yang" rhyme) or short, dim sounds (called "yin" rhyme). The choice of this rhyme determines the mood of the poem, similar to the choice of a major or a minor key in music.” *
The Yan Yun "masculine" aftertaste of, say, a Ruo Gui rock tea, classically lingers for a long time. It gives you the clear bright impression you would expect from activation of TRPA1, the trigeminal cold receptors in the throat.
By contrast, Tie Guan Yin gives a sweet, gentle, more muted after-taste—breathy rather than clear—the quality that Pulleybank and his colleague ascribe to the Yin speech tones in Chinese.**
Here is a Chinese poem about tea, with translation and important-to-read notes at http://chadao.blogspot.com/2009/04/song-dynasty-tea-poem-zhu-xis-tea-stove.html
茶灶 朱熹 CháZào -- Zhū Xī (1130-1200 CE)
仙翁遺石灶 xiānwēng yíshízào宛在水中央 wǎnzài shuǐzhōngyāng飲罷方舟去 yǐnbà fāngzhōuqù茶煙裊細香 cháyān niǎoxìxiāng
'Tea Stove' by Zhu Xi
Stone stove left behind by immortals,Lies crooked in the center of the stream.
Tea finished, two boats drift on abreast,Tea smoke; wafting delicate fragrance.
The "grave accent" in pinyin indicates the short breathy falling tones of a "Yin" rhyme...
...and here is a photo of the Nine-Bend River in Wuyi, the location of the poem, by Zhangzhugang, Wikipedia, CC BY-SA 3.0 license.
(Incidentally, notice the orange-red color of the Wuyi rocks. It comes from the presence of iron. Excess iron causes tea plants to produce kaempferol, a flavonoid that binds up the iron so it doesn't damage the plant. In your mouth kaempferol activates TRPA1—the cause of the Yan Yun effect of Wuyi rock tea.)
* Ray Wen Wei . Chinese classical poetry is based on universal principles of singing. EIR Volume 19, Number 13, March 27, 1992.
**E. G. Pulleybank and 蒲立本. “The nature of the middle Chinese tones and their development to early Mandarin/中古汉语声调的本质和到早期官话的演变. Journal of Chinese Linguistics, vol. 6, no. 2, 1978, pp. 173–203. JSTOR, www.jstor.org/stable/23752830.