Why "Red Sorghum" as played by Jiang Wen has become a classic?

Remember the Shaanxi folk song "Sister you boldly go forward", which appeared three times in the movie, and these three times in different scenes, the same song was sung in different moods. After Yu Zhanao forcibly possesses Jiu'er, Yu Zhanao sings the song for the first time, as if telling Jiu'er, "Don't be afraid, everything is with me." The second time appeared in Yu Zhanao drunk and disorderly, haphazardly said in the sorghum field and Jiu'er happened, and then by Jiu'er let someone throw into the wine tank inside, Yu Zhanao in the wine tank with three days and three nights, this time sang the song, as if inquiring, "Why is it like this?" . The third time is after Jiu'er was killed by the Japanese, the movie, which was originally a red-based movie, shows a sunset landscape that is even more red, and this scene impresses me to this day. And in such a scene, and Yu Zhanao sang the song again, as if to comfort the nine children, do not worry about the child, there he is, but also for the nine children deep love.