I had this thought. At many times, Mat inadvertently speaks in the Old Tongue, not knowing what he is saying or even that he is saying it.
I envision a point where he meets the Mahdi and the memories in his head spout out the requested song with no overt recollection of where it came from.
Oh, I have no doubts that the Mahdi will ask someone at last if they know the song and Blessedly! , someone will finally be able to tell him yes.
The Song will one of rejoicing and reconciliation and they will find it among the Wise Ones. I have no doubts that the Song is known to them and the...