J. K. Miller underwent Montessori Elementary Teacher Training in Bergamo, Italy, and concurrently received music education based in Montessori method instruction from Fresco-Galeazzi, who had been a student of A. M. Maccheroni. Miller is currently a trainer at the Montessori Elementary Teacher Training program organized by the Association Montessori Internationale. Miller developed a music curriculum in the Montessori method by expanding and modernizing the music education theory of M. Montessori, Maccheroni and E. B. Barnett. The current study aimed to clarify the position of children’s musical expression in Miller’s version of the Montessori method. In this research, we focused on the “Musical Instrument” and “Games and Musical Expression” areas of the program, including elements of musical expression of young children in Miller’s music curriculum. Analysis of children’s musical expression in Miller’s method revealed two main features: (1) collaborative activities are intended to develop children’s ability to express themselves through music; and (2) the process of expression and creative activity itself is emphasized. In addition, our results revealed that musical expression in Miller’s method contributes not only to mastering musical abilities and skills, but also to fostering “creativity” as a core component of the Montessori method.