In ORGANUM, the presence and displacement of visitors activate one or more videos of a woman who sings in the Villers Abbey (Belgium), one of the most famous medieval ruins in Europe. In addition, the interactor can slow down the video and sound with her displacement. Whenever she activates a new video, this is superimposed with the previous video for 5 seconds, in order to produce an ephemeral polyphonic experience. For the polyphony to continue, it is required more than one interactor at a time. The singing is inspired by the medieval sacred chants, more specifically the polyphonic music of the Notre Dame school. In ORGANUM, the body and movement of the visitor produces a unique introspective and meditative music.