This study aims to develop lessons in which diversity and collaboration are assured through children’s cooperative involvement. Today we should build a system of inclusive education against the background of the social need for all students to exercise their abilities. We framed teaching plans according to children’s difficulties, accommodated their learning environments, and encouraged them to cooperate with each other via their strengths. We then performed activities in different class types: (1) a special needs class for students with diverse disabilities, (2) classes of 4th graders, and (3) a combined class of lower graders in the primary school. We found that (1) creating a piece of music with their own handmade instruments, (2) learning by following others, and the use of kakegoe and shoga, and (3) the opportunity for the creation of students’ own ideas for playing an instrument, reduced the students’ difficulties and helped them to accept each other.