In case you’re not familiar with the concept, every language is slowly changing over time. So not only would the vocabulary and grammar of a language be different if you were able to go back in time and observe, but so would the actual pronunciation. The farther back you go, the bigger the change. As you can imagine, it’s difficult work piecing together the ancient pronunciation of a language when there are no audio records.
I can’t vouch for the accuracy of these videos (I don’t know much about ancient Chinese poetry), but they’re certainly interesting. Try showing them to a Chinese friend and see what kind of response you get. (It’s my impression that while the Chinese are well schooled in ancient poetry, they are often pretty clueless how different the ancient pronunciation of that poetry actually was. It’s not just a tone here or there!)
李白 靜夜思 中古漢語朗讀