Why do ancient poems emphasize the level and rhyme so much?

Classical metrical poems have strict requirements on the level and fluency of words, which is known to those who are slightly familiar with ancient Chinese. Take the Seven Laws as an example. In the first connection, parallel connection, neck connection and tail connection, it is especially required that the middle two connections be strictly opposed. This antithesis is not closely related to the number of words and the part of speech, but also related to the tone. Tone, first of all, is flat, that is, there can be no continuous flat or flat tone. Of course, this requirement is only for even numbers, that is, the so-called 135 is not divided, and the 246 is clear. Secondly, there is a connection between couplet and inline alignment, that is, the post-couplet sentence is the same as the pre-couplet sentence, and the post-couplet sentence is flat and opposite. There are more tag formats of words, and the forms of flush words are more complicated, but flush words are still an important principle. For words, only words that conform to the level of words can be placed in a fixed position. Poetic quatrains and various fixed forms of lyrics and songs (including specific requirements in terms of the number of sentences, the number of words, antithesis, rhyme, level tone, etc.) all have their own distinct aesthetic and poetic characteristics. The quatrains of metrical poems consist of five words and seven words. On the one hand, they have a distinct reading rhythm, on the other hand, they are more in line with the requirements of memory psychology. This sentence structure is the easiest to remember. Dui has a typical axisymmetrical aesthetic feeling, which coincides with the aesthetic characteristics of China culture. For example, the typical feature of ancient buildings is axial symmetry; Consistent rhymes can make reading and reciting harmonious and smooth; The alternation of flat and flat makes the poem cadence; Even the poem can link the tone of the whole poem, which is similar to the thimble in China's rhetoric. The importance and necessity of various fixed morphological features can also be seen that they are not equivalent. For example, rhyme, even modern Chinese poetry has such a requirement. This shows the importance of rhyme in poetry expression. Comparatively speaking, where is the importance of leveling? What is the essence of leveling? Tone is unique to Chinese, and it is an essential phonetic feature of Chinese characters, unlike English words, which have only syllable features and no tone (the so-called tone in English is not the defining factor discussed here at all, so I won't go into it). The essence of tone is the changing characteristics of pitch and rising and falling length when a word is pronounced. In Mandarin nowadays, the flat tone is Gao Pingtiao (not rising or falling), the upper tone is upper-middle tone (not high or low), the upper tone is low and the falling tone is high. Simply put, tone sandhi is tone sandhi. But word of mouth, so the historical changes in 2008 changed greatly, and there were regional differences, which made it difficult to unify, unlike the fixed circulation form of words, which was relatively stable. At present, the tone of Yin and Yang in Putonghua is classified as Ping, the tone of upper voice is classified as Nuo, the ancient rhyme is classified as four tones of upper voice and the tone of upper voice is classified as Nuo, which is different from today's tone classification. Its specific pronunciation cannot be known in detail. An editor talked about the wet words in my poem "Sitting and Watching Cold Mountain Wet", and thought that they belonged to the category of entering tone and falling tone, which was true in ancient rhyme. It is true that today, there are still many local languages with entering tones, just like the ancient sounds, which are different in different regions. However, Rusheng has now been deleted from Putonghua, and the original Rusheng characters are classified into four tones: Yin and Yang. According to the new rhyme, the word "wet" is called level tone, which belongs to the level tone category. Then, in the creation of modern ancient poetry, should Putonghua be the standard, or should the ancient sound be the standard, or should the local sound be the standard? If there is a standard, of course, it should be based on having the largest number of users or having Mandarin designated by the state. There are seven poems of the Tang Dynasty in Liangzhou Ci (in fact, there are no poems, but some critics' words are used to illustrate the important position of this poem). "Why should the Qiang flute complain about the willow" and "flute" are a kind of falling sound in ancient times. Today, Mandarin is rising, flat and out of line; And the word "Yang" is flat, which is also out of line. This also shows from the side that the requirements for leveling can't be too strict, because sometimes we can't completely determine the unified standard of leveling. As can be seen from the secondary facts, Pinge has great flexibility in the creation of quatrains. Poems read in ancient pronunciation are read by the standard of Putonghua today, many of which are out of line, but we still appreciate them and don't think there is anything wrong with them. Why? Because we pay attention to the richness of poetry content and the beauty of artistic conception, but ignore the level of levelness, it can be seen that the importance of levelness is indeed secondary. Ancient poetry can be sung with joy. Poetry is recited, not sung, but lengthened pronunciation and changed tone. This is a way of reading. Ci also has the theory of composing ci by sound, and the actual epigraph is a song that has been composed. Once ancient poetry is put into music or recited, its tonal nature ceases to exist, and even words lose their meaning. Only when it exists in the form of pure language, leveling will have certain significance. From the perspective of intonation or appreciation of poetry, the aesthetic characteristics of flat tones in poetry are not necessarily necessary, that is, the role of intonation in the creation of ancient poetry should be mainly to define what a word is, and only correct reading can judge it, rather than fixing flat tones or flat tones in this position. Obviously, this requirement should not be as strict as the requirement of symmetrical beauty in architecture. When a famous vocal tutor sings the difference between "violinist" and "animal", he asks the former to have a soft voice and the latter to distinguish it with hardness. Light tone refers to the gradual enhancement of pronunciation from weak to strong, similar to rising tone or rising tone, while hard tone refers to the sudden uniform sound, similar to falling tone pronunciation. Comparing the sound intensity with the pitch, it also shows that Chinese characters have lost the meaning of tone when entering music and cannot be used in other aspects. Another way to deal with singing is to add an offset according to the flat tone of the word before pronunciation. In the actual language expression, Chinese words are also in flexible changes, such as the light tone in conjunctions such as disyllabic feet (there are many places where light tone appears); Tone sandhi of several words in 178 (first, before the flat sound, read it as a flat sound, first, before the flat sound, read it as a flat sound); Two voices (such as the word ideal), the previous voice becomes a semi-voice, and so on. In a specific context, individual creativity will change. I've heard that when a football goal is scored, the commentator is excited about the word "strike", sometimes pronouncing it semitone, and sometimes pronouncing it directly as an ascending tone. These flexible changes have greatly enriched the expressive ability of Chinese, and at the same time, we can see that in poetry, even words can also have flexible and diverse applications. It is far-fetched to insist that the flat and even sentence pattern "flat and even" is more beautiful and wonderful than "flat and even". Because the use of flat tones in metrical poems is mainly due to the need of form, its aesthetic significance is not great. Therefore, in order to get a good inheritance and development in modern times, metrical poetry should take into account the importance of its various formal features, appropriately relax the restrictions on flat lines, take flat lines into account as much as possible without hurting the meaning, and even abandon the shackles of flat lines to be flexible. Perhaps this is the fate of metrical ancient poetry in modern times.