What was the original function of the embryonic Chinese characters?

The embryonic Chinese characters were originally used to record sounds and tones. For example, ancient rhyme books and rhymes recorded syllables and tones in the form of Chinese characters. As time passed, the prototype of Chinese characters gradually developed more functions, such as expressing phoneme, syllable, tone, meaning, and so on. In the process of the evolution of Chinese characters, many embryonic Chinese characters evolved into formal Chinese characters, which became the foundation of modern Chinese characters. For example, the initial form of "Xu" was "Yan", which meant speaking, and later evolved into "Yu", which meant language or speech; the initial form of "Song" was "Shi", which meant poetry or praise, and later evolved into "Song", which meant praise or praise.