| Taking thirty-two Beethoven piano sonatas as examples, this paper presents a thorough investigation on period structure. Since the notion of period has been defined and interpreted quite differently in different theoretical textbooks and writings, in this paper, a comprehensive overview of existing literature is offered to properly interpret the characteristics of the theoretical framework of each writings, on the basis of which the difference and connection of the interpretation of relevant concepts like period, phrase, and double phrase in those writings are clarified. Then, Beethoven piano sonatas are taken as cases to probe into the distinctions among the period structure of different movements. |