§ Of the Return of the Noldor The Silmarillion

Then Fingon the valiant, son of Fingolfin, resolved to heal the feud that divided the Noldor, before their Enemy should be ready for war; for the earth trembled in the Northlands with the thunder of the forges of Morgoth underground. Long before, in the bliss of Valinor, before Melkor was unchained, or lies came between them, Fingon had been close in friendship with Maedhros; and though he knew not yet that Maedhros had not forgotten him at the burning of the ships, the thought of their ancient friendship stung his heart. Therefore he dared a deed which is Justly renowned among the feats of the princes of the Noldor: alone, and without the counsel of any, he set forth in search of Maedhros; and aided by the very darkness that Morgoth had made he came unseen into the fastness of his foes. High upon the shoulders of Thangorodrim he climbed, and looked in despair upon the desolation of the land; but no passage or crevice could he find through which he might come within Morgoth's stronghold. Then in defiance of the Orcs, who cowered still in the dark vaults beneath the earth, he took his harp and sang a song of Valinor that the Noldor made of old, before strife was born among the sons of Finwë; and his voice rang in the mournful hollows that had never heard before aught save cries of fear and woe.