One of the most important recommendations in the 17 Sustainable Development Goals (SDGs) adopted at the UN Summit in 2015 was "No one will be left behind". Canadian composer R. Murray Schafer pointed out that the dominant form of music education in training musicians is Romantic or Dionysian. Schafer finds this type of music education subjective and hedonistic and develops the concept of soundscape and sound education to enable "public" traffic between the sound environment and the children. Schafer's goal was to realize the social welfare element of sound or a Universal Design. To modify the Dionysian approach to music education and to construct a type of public music education based on physicality and Universal Design, the Japanese music educators and academics Shigeshita, Tsubonou, and Murao referred to music that assumes a virtual external audience (such as a club-type class chorus) as "music of the stage" and proposed that the "music of the square" is the opposite concept. This concept has affinities with Schafer's sound education. This paper aims to explore how music education should be developed in keeping with the goal of "no one will be left behind." For this, the future reconstruction of music is examined through an action research and philosophical studies based on sound education by Sumie Tonosaki, which was conducted at a school for the deaf in Aomori Prefecture from 2014 to 2016. Action research was conducted in a joint class of an elementary, junior high, and special needs school in Japan through a class titled, "Let's create a new soundscape by finding existing sounds," held in October 2021, in collaboration with children with special needs, elementary, and junior high school children of the Faculty of Education at Hirosaki University, based on the following practical activities: 1) experiencing environmental sounds via a soundwalk; 2) recording sounds of interest with a tablet device; 3) uploading recordings to the cloud; 4) converting URLs into QR codes; 5) exchanging QR codes between schools; and 6) playing sounds with a tablet device and improvisation (steps 3 and 4 were completed by teachers). The results revealed the possibility of an equal and creative classroom practice for deaf, elementary, junior high, and special needs children.