“调”是中西乐学理论中的一个重要概念，但中西乐理对“调”的表述则说法不一，致使“调”在乐种学中的意义一直未引起人们应有的重视。本文提出：“调”就是乐种的自然音列及这个音列所在的音高位置。自然音列是乐种在律的基础上所作的乐音材料和音程材料的选择，并按照“若干度若干音”的音列形式固定下来的乐音序列结构。 “Tune” is an important concept in the theory of music in China and the West, but Chinese and Western music theories have different opinions on “Tune”, which makes the meaning of “Tune” in the study of musicology has not given due attention. This paper proposes that “tone” is the natural tone of music and the pitch of the tone. The natural soundtrain is a musical tone sequence structure that is fixed by the musical instruments based on the law and selected from the musical material and the interval material, and is fixed in the form of a musical soundtrack of “several degrees of certainty”.