Demise Is The Voice Zelda Hears Throughout The Game?

 Redditor /u/Moryak_the_brass believes the disembodied voice that speaks to Princess Zelda throughout the game (the voice of the Master Sword) belongs to Demise, the Skyward Sword big baddie. Skyward Sword ends with Link defeating Demise, who becomes incorporeal and is absorbed by the Master Sword, which traps him. Fi is the voice of the sword in that game, but Fi also says she would "...enter a sleep without end," meaning her voice would no longer speak to the outside world. Who then is speaking from the sword? This Redditor believes Demise is manipulating Zelda in an effort to escape the sword.