Yangguan San Die (Adios at Yangguan) is a piece of music played with Guqin according to a poem written by Wang Wei, a famous poet in the Tang Dynasty (618-907).
Wang Wei wrote the poem when he saw off a friend to serve in army at Weicheng, a small town in Yangguan neighboring the border.
The poem goes like this: "In the central town Weicheng, it rains lightly in the morning. All the houses and the willows look fresh after the rain. I suggest you have another cup of wine, as soon as you go out of the Yangguan Pass, there are no friends."
Instrument players made it a see-off song based on the poem. Even today, some people usually sing this song when they see off friends.