In Imperial China, emperors and other high officials sometimes disguised themselves as commoners and mingled with the ordinary folk to learn what they were really thinking. For essentially the same purpose, a government office in the People’s Republic now collects shunkouliu, or “slippery jingles.”……Uncensored and uncensorable, they are the freest and arguably the liveliest medium in China, even though the government has classified the poems in its own collection as state secrets.
Perry Link has a very brief piece in the Washington Post on collecting songs in China.
Isn’t “shunkouliu” just rhymes ?
By the way, when emperors and high officials disguised themselves and mingled, they did more than just “learn what they were really thinking”. There were plenty of examples of illegitimate offsprings were involved.