Introduction to the tragic song of passing the pass: After Meng Jiangnu set out on the road and walked for several days, she came to a pass. Just as she was about to pass the customs, the soldiers guarding the city asked her to pay customs duties. Meng Jiangnu had walked such a long way and had no money left. The soldier said, "Since you don't have money to pay customs duties, sing a song for us!" "Meng Jiangnu had no choice but to sing a song for them - the December Tragedy with tears in her eyes. She sang with such sadness that the soldiers were moved. So he let her pass.