The first sentence, "The Yellow River is far above the white clouds", captures the characteristics of overlooking and depicts a moving picture: on the vast plateau, the Yellow River rushes away, looking far to the west, as if merging into the white clouds. The second sentence, "An isolated city, Wan Ren Mountain", is about an isolated city in the fortress. A lonely city located in the frontier fortress, standing tall by mountains and waters. These two sentences describe the majestic momentum of the motherland's mountains and rivers, outline the geographical situation of this important national defense town, highlight the desolate situation of foot soldiers guarding the border, and provide a typical environment for the latter two sentences to describe the psychology of defending the army.
In this environment, I suddenly heard the sound of Qiangdi, and the tune I played happened to be "Folding Willow", which aroused the sadness of the garrison. The ancients had the custom of parting and giving gifts. "Liu" and "Liu" are homophonic and presented to Liu as a souvenir. In the Northern Dynasty Yuefu's "Blowing the Drum Horn Across", there is "Folding Yang Liuzhi", and the lyrics say: "If you don't catch the whip when you get on the horse, you will hit Yang Liuzhi instead. Dismount and play the flute, worrying about killing travelers. " It is mentioned in the song that pedestrians break willows when they walk. This kind of farewell wind was very popular in the Tang Dynasty. Thus, there is a close relationship between willow and parting. Nowadays, when the frontier soldiers hear the sad tune of "Folding Willow" played by Qiangdi, it is inevitable that they will feel sad but not hate it. Therefore, the poet explained in an open-minded tone: Why does Qiangdi always play the sad tune of "breaking willow"? You know, outside Yumenguan is a place where the spring breeze can't blow, and no willow can be folded! To say "why complain" is not to complain, nor to persuade the guards not to complain, but to complain is useless. The use of the word "why complain" makes poetry more subtle and meaningful.
-from the encyclopedia