Look at the movie "Summer Concerto". In the piano song "I Know" (played by Yan Weiling), Wang Baoqiang and Xu Zheng went to give money to the female teacher while they were in embarrassment, and the background music behind it was very... The sad piano music is a variation version of "I Know", which is very nice. It is also the music played when the two were taking a ferry on the Yangtze River.