Taking account of the events in the game Skyrim. The voice was taught by Paarthurnax (possible observer) to the Greybeards (rebel). Then fast forward time to the LDB. Who was shouted at by the Greybeards (after taking a dragon soul). Then a time later the LDB kills Alduin.
Also Shor being absent from his throne, maybe he was manifested in the LDB from the first greybeard shout?
And Dagon knew that where the horn soundings landed, the Tongues of High Hrothgar could step, and, when together, the greybeards could breathe unto being the ghost of Shor, which lay all Powers low [even in half-death].----http://www.imperial-library.info/content/seven-fights-aldudagga
Is it possible that Shor has mantled the LDB to overcome Alduin?