My son used to play a Chopin Waltz, but I am not sure which one he played. When he learned that piece we didn't have a digital camera, so recordings left. It is great to go to a master class. My son is going to have his first master class tomorrow. I hope my son can make a friend with yours. If you go to Youtube and search for "Nathan Qi", you will find all of recordings we have right now. Please let me know of your son's Youtube channel if he has one. They can be friends on Youtube.
P.S., I reposted the video today together with "Cat and Mouse".
Wish your son have a wonderful competition, and please for sure to share with me the good news!