Josef Svoboda "described a scenography for a proposed production of Faust in 1970 with director Alfred Radok, in which a crucial conceptual understanding was that Mephistopheles and Wagner, Faust's student and domestic servant, were one and the same person, and, of course, one and the same actor. The stage box was an empty and seemingly void space, shaped only by huge, very dark brown, barely distinguishable wall surfaces to the back and sides. The stage floor was steeply raked and apparently flagged with stone. A crucial feature of this floor was that beneath the stage were to be fitted felt-covered 'dampers' that could, by the action of the silently operating pistons, be made to press against the under-surface of the stage and render it silent. As Faust prepared his occult pentagram down stage to 'conjure' diabolic forces, the stage would echo with the sound of his and Wagner's footsteps. Wagner, however, would not engage or assist in Faust's conjuring practices; he would turn and make to elave, walking up stage, and his echoing foosteps would be heard. As he reached the farthest limit of the stage he would turn and walk back down the stage in total silent to stand before Faust – everyone in the theatre would know that in that transition of sound from echoing noise to silence he had become Mephistopheles."
from Theatre, Performance and Technology by Christopher Baugh