I was reading The Story of Myrddin Wyllt (which appears to be another name for Merlin and the Five Dreams of Gwenddydd), written by Elis Gruffydd. It concerns Myrddin Wyllt, who is identified with Merlin by later authors. What's curious is that it mentions Myrddin's father, a human, while many other tales claim that Merlin's father was an incubus:
According to the narrative of some authors there was about this time within one which is called Nanconwy a man who was called Morfryn. But others show this was Morfryn Frych, prince of Gwynedd, - which he could not be according to the tenor of his songs. Nevertheless the writing shows that a man of this name had a son who was called Mryddin son of Morfryn (. . .)
The second sentence puzzles me:
which he could not be according to the tenor of his songs.
I haven't been able to find any other good versions of Gruffydd's narrative, so I don't have anything to compare this wording to. What does "the tenor of his songs" mean? What is Gruffydd trying to say about Myrddin's human father?