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!
Suwu herding sheep played by Song Fei (2017)
Source. 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.