The purpose of this study is to clarify children’s musical development and changes in feelings and values until they complete learning the music. To elucidate this process, I acted as a participant observer in the activities of the Kurashiki Youth Chorus and they completed a questionnaire survey. The data were analyzed based on the grounded theory approach. As a result, the children’s impression of the beginning of the song changed and deepened through their practice process. Through the training process, the children were able to express the inner nature of music and their image of the music in their own words with diversity of expression.