An illustration of the battle of song between Sauron and Finrod Felagund on the isle of Tol-in-Gaurhoth.
"Thus befell the contest of Sauron and Felagund which is renowned. For Felagund strove with Sauron in songs of power, and the power of the King was very great; but Sauron had the mastery, as is told in the Lay of Leithian:
He chanted a song of wizardry,
Of piercing, opening, of treachery,
Revealing, uncovering, betraying.
Then sudden Felagund there swaying
Sang in answer a song of staying,
Resisting, battling against power,
Of secrets kept, strength like a tower,
And trust unbroken, freedom, escape;
Of changing and of shifting shape,
Of snares eluded, broken traps,
The prison opening, the chain that snaps.
Backwards and forwards swayed their song.
Reeling and foundering, as ever more strong
The chanting swelled, Felagund fought,
And all the magic and miht he brought
Of Elvenesse into his words.
Softly in the gloom they heard the birds
Singing afar in Nargothrond,
The sighing of the sea beyond,
Beyond the western world, on sand,
On sand of pearls in Elvenland.
Then the gloom gathered; darkness growing
In Valinor, the red blood flowing
Beside the Sea, where the Noldor slew
The Foamriders, and stealing drew
Their white ships with their white sails
From lamplit havens. The wind wails,
The wolf howls. The ravens flee.
The ice mutters in the mouths of the Sea.
The captives sad in Angband mourn.
Thunder rumbles, the fires burn –
And Finrod fell before the throne.
Then Sauron stripped from them their disguise, and they stood before him naked and afraid. But though their kinds were revealed, Sauron could not discover their names or their purposes.”
— J.R.R. Tolkien, "Of Beren and Luthien," The Silmarillion