So in other words everyone is an idiot
If what Anduin said was true, and the radiant song is really coming from Beledar, the crystal in Hallowfall... and then the Eyes of the Earthmother says this: "The tauren believe that the Earth Mother shaped the world to be a sanctuary where she could give birth to "the light of her heart"" and "The next time she slumbers, she stretches over the land so that the beating of her heart digs into the earth, saturating it with "the song of life"" then this means this crystal is the earthmother's heart. The heart of Azeroth.
I don't think it's obvious the voice is coming from the world soul. I think Blizzard is making a point of showing how this voice is unlike the one Magni heard, and that is being done to show us we need to suspect those voices. Either the new voice is not our world soul, or Magni was not being guided by our world soul originally. Hope we get more detail soon =)
Maybe it's referenced to Azshara?