Serge Ermoll is the correct spelling (although it has been spelled Sergei Ermolaeff. A five minute search turned up this..welcome to the Chan Family Forum
Serge Ermoll is the son, who recently died. But when the family wanted to leave China, They went from Shanghai via Hongkong to Australia. Probably during this time Serge Ermolaeff (senior) composed the music to some of the films.
I'm hoping to find his name in the credits, but I don't want to buy all the movies......