In ancient times, people didn't write poems with words. At that time, there was also a dictionary for finding phonology, which was called "rhyme book" in ancient times. Ancient rhyme books organize Chinese characters according to the relationship between sound, rhyme and tone, but the key point is to divide the rhyme parts of Chinese characters. In ancient times, with the changes of the times, people's understanding of rhyme has been continuously improved, and many rhyme books have appeared. Among the more orthodox official rhymes, Guang Yun, Zhongyuan Rhyme and Lue Yi Tong Yun are very representative, and the three rhymes have different definitions of rhyme.
For example, Guang Yun is classified according to the tones of Chinese characters, and then divided into rhymes under each tone, and then arranged according to the words appearing at the same time in each rhyme; The rhyme division of Zhongyuan Rhyme, each rhyme division is separated by tones, and then arranged according to the simultaneous words in each tone; "Yun lve Yi Tong" is also divided into rhyme parts first, but each rhyme part is classified by initials, and then arranged separately in the same word according to tone.
In fact, no matter how they are arranged, they are all based on the sound, rhyme and tone of Chinese characters. These rhyme books have summed up the rhythm of Chinese characters very carefully and fully. However, by the time this cognition was reached, it was already the Song Dynasty. So, before these rhymes were finalized, how did people divide the rhythm when writing poems?
To say "anti-tangent" and "four tones" is the basis and necessary condition for the emergence of rhyme books. To put it bluntly, backcutting is the phonetic notation of ancient Chinese characters, which is to spell out the pronunciation of another Chinese character with the help of two words. For example, "Juzhi" is pronounced as "Mo", in which "Juzhi" is a word-cutting, "Zhi" is a word-cutting, and "Mo" is a word-cutting. In other words, the pronunciation of the word-cutting is spelled with the sound and rhyme of the word-cutting.
The emergence of "four tones" is related to the pursuit of Chinese phonology by ancient literati. At that time, some poets who paid attention to the rhythm of poetry wrote works in this field, which were contained in Gao Zhuan and Wen Jian Ji, while others created Four Tones and Four Tones Spectrum to annotate the four tones of Chinese characters.
That sounds complicated. It is not entirely correct to say that there was no pinyin in ancient times. The "backcutting method" can accurately read Chinese characters. In addition to anti-cutting, there are cutting and reading methods, which are similar to the ancient methods of pronouncing Chinese characters in modern Chinese Pinyin. Rhyme is equivalent to checking pronunciation.