The main four instruments are undoubtedly:but there is also amazing content on others which must not be missed, including:
Infinite Wikipedia instrument list: en.wikipedia.org/wiki/List_of_Chinese_musical_instruments
www.ibiblio.org/chinese-music/html/traditional.html contains an amazing orchestral version for di flute TODO identify! When attempting to upload to YouTube, it identifies as "Su Wu Tending the Sheep" and give a name "Chen Tao", but no further information. Chen Tao is presumably this dude: www.barduschinamusic.org/chen-tao-dizi | www.melodyofdragon.org/chentao.html 陈涛
baike.baidu.com/item/苏武牧羊/5532#11_2 mentions that it comes from an erhu concerto composed by Peng Xiuwen
The sadness of the erhu perfectly fits the role and mood of the story! Brilliant!
baike.baidu.com/item/江河水/1634212 Baidu Baike page. Originally composed for two pipes, but was later adapted to the erhu in 1962 by Huang Haihuai.