Chinese symphony music can be traced back to Xia dynasty (2070–1600 BC), where various bronze-based percussion instruments (such as Bianzhong and Nao) were played at the emperor’s palace during important ceremonies. As history moved on, more types of instruments (string, plucking, percussion) were created and gained popularity as a format of folk music. Many of these instruments were based on wood, animal’s bone, skin and hair, as well as steel. The formation of these instruments was heavily influenced by a variety of regions including Persia and Mongolia. And at the same time, the development of Chinese musical instruments also tremendously influenced the development of musical instruments. Therefore many oriental instruments (such as Zheng) exist in multiple countries with small instrumental design variations and diverse musical styles. In the modern days, Chinese symphony music has become more influenced by western music. As a result, more music pieces are composed based on heptatonic scale instead of the traditional pentatonic one. Western instruments are also introduced into Chinese symphony pieces.