We know how Chinese was pronounced 1400 years ago thanks to the world’s oldest surviving rhyming dictionary.
The English language is written in an alphabet, and that makes it relatively easy to work out how words used to be pronounced. We know, for example, that the k at the start of “knight” was not always silent, nor was the gh. (My Middle English is a bit rusty, but I believe that if you say the German word “ich” with a “kn” at the front and a “t” at the end you’d be pretty close.)
Working out how words used to sound in Chinese is a whole lot more difficult. The Chinese language is written with logograms: a symbol typically equals a word, not a sound, so we have no frame of reference for how each word may have been pronounced. No frame of reference, that is, except for the world’s oldest surviving rhyming dictionary.
Cut to 6th century CE China. Eight literary friends were having a party. Wine flowed, tongues loosened, and someone complained about the difficulties of pronouncing poetry properly. I think I’ve been at a party like that. China – then, as now – was awash with different dialects. Even among this small crowd of eight, five different dialects were present. But these were scholars, learned people, so rather than just complain they decided to do something about it. Then and there, they began sketching out plans for a dictionary organised not by symbol but by sound.
It took twenty years for one of the scholars from that party, Lu Fayan, to publish his rhyming dictionary. The 601 CE text Qieyun was important because it tells us today just how words from Middle Chinese would have been pronounced. Well, sorta. Because it represents how a bunch of scholars thought poetry should be pronounced, and also attempted to merge several different dialects to create some harmony and consistency, it requires some serious modern scholarship to untangle its relationship to actual regular speech of the time.
It wasn’t the first rhyming dictionary ever – that would be the Shenglei, which was written around 230 CE and was lost forever in the 13th century CE – but it was certainly the most influential: Qieyun was republished, refined, and expanded for hundreds of years afterwards. It is still the starting point for our understanding of the sounds of Middle Chinese.