The Scary Folklore: Ura no Sho 2007 on netflix

Five years have passed since 12 members of the choir were brutally murdered in the music room of Seiran Jogakuin, a prestigious school in the suburbs of Tokyo. A TV news crew visits the scene to clarify the rumor that children’s songs can be heard from coming from the closed school. Accompanied by Kyoko, an acoustic analyst, the team begins their own investigation into the incident, but one after another, strange things begin to happen to the staff…