After having presented musical instruments formed by humans striking the ground, using cavities either embedded in the ground or formed by the feet as resonators, in Chapter 4 Schaeffner extends this part of his thinking to the ground used as the material base for theater. Accordingly, he offers a brief overview of the organology of theater. Thus, the floor of the stage acts as a soundtable, and by extension, the theater in its entirety forms a vast resonator whose structure is like that of musical instruments. After the amplification of the sound of steps, there naturally follows the enlargement of the voice and of all the sounds of the action, as well as the sounds of the emotions it elicits.