阳关三迭 — “An ancient melody for bidding farewell, often sung with repetitions”

During the Tang Dynasty, Liu Yuxi, a high-ranking official, would pass a humble dwelling daily on his way to court. There, he often heard a pancake seller mournfully singing Wang Wei's famous poem, 'Weicheng Qu,' which includes the poignant lines: 'In Weicheng, morning rain dampens the dust, by the guest house, willows are fresh and green. I urge you to drink one more cup of wine, for west of Yangguan, you'll find no old friends.'

Moved by the man's singing and the sentiment of the song, Liu Yuxi gave him ten thousand coins to expand his business. After that, he never heard the man sing that sorrowful tune again.

The repeated singing of the 'Yangguan' part of the poem during farewells became known as 'Yangguan San Die'.