What are the similarities and differences of
Japanese and Korean music?

Their cultures are highly influenced by traditional Chinese culture. In ancient Korea and Japan, educated people learned the Chinese characters and they expressed themselves in written Chinese, and their languages evolved from  Chinese characters.  It was the language of the elites. Both societies also absorbed the ideas of Confucianism, the most important political philosophy of China. And finally, both are Buddhist countries. Buddhism came to Korea from China , and it made its way to Japan from Korea.  Daoism and Buddhism are two major religions in China.