Chinese musicology is the academic study of traditional Chinese music. This discipline has a very long history. Traditional Chinese music can be traced back to around 8,000 years ago during the Neolithic age. The concept of music, called 乐 (Chinese: 樂; pinyin: yuè), stands among the oldest categories of Chinese thought; however, in historical sources, it does not receive clear definition until the writing of the Classic of Music (lost during the Han dynasty). Different musical traditions have influenced it throughout its history, dating back to the Xia and Shang dynasties [citation needed].