§ Of Beren and Lúthien The Silmarillion

Upon Doriath evil days had fallen. Grief and silence had come upon all its people when Lúthien was lost. Long they had sought for her in vain. And it is told that in that time Daeron the minstrel of Thingol strayed from the land, and was seen no more. He it was that made music for the dance and song of Lúthien, before Beren came to Doriath; and he had loved her, and set all his thought of her in his music. He became the greatest of all the minstrels of the Elves east of the Sea, named even before Maglor son of Fëanor. But seeking for Lúthien in despair he wandered upon strange paths, and passing over the mountains he came into the East of Middle-earth, where for many ages he made lament beside dark waters for Lúthien, daughter of Thingol, most beautiful of all living things.