on the discussion of "the sound" , the way the final days (in the present) where presented it looked more like meteions song of oblivion or whatever its called in english enabled the transformations but still needed a trigger to activate. if i'm not completly wrong right now than Pandemonium is in fact far below the ground and potentially? going deeper the further we go. considering every raid storyline so far while not absolutely necessary to complete did in fact have some tie ins to the mainstory it certainly is possible that "the sound from below" would in fact come out of Pandemonium and act as a catalyst for meteions song.