I learn erhu. Seinfeld plays erhu very well. Almost every picture is classic. If your father is studying erhu, I suggest you buy some famous music albums. For example, Erquan reflects the moon, horse racing, Honghu theme capriccio, ripe grapes, rivers, and so on, and many more. If you are not a professional and just like erhu, you can buy some familiar tunes, such as Liang Zhu and so on. It is more in line with the tastes of people of their time.

PS: Very filial! I wish your father happiness!