The aim of this study was to explore the use of in-between spaces to create music environments in a preschool setting. The research method was a 1.5-year case study of a preschool in northern Taiwan, focusing on innovative music environment creation in the in-between space. The implementation process was divided into three stages: exploration, development, and maturity. Children were free to interact with the environment during school hours. Data were gathered through observations, interviews with children, teachers, and the principal, as well as a review of parent-teacher communication books and children's works. The findings indicated that the in-between space not only had a great impact on children's development but also enhanced their aesthetic experiences, effectively achieving educational goals. Proper utilization of in between in preschools has the potential to create substantial added value. Designing music environments that leverage their unique characteristics can establish an adaptive and engaging music learning environment for children. This allowed children to unleash their creativity and cultivate habits of independent learning through free play. However, a successful music environment required systematic planning and execution, setting goals in stages, and guiding children through a gradual music experience.