The Silmarillion, Ainulindale, by J.R.R. Tolkien, pages1-2

There was Eru, the One, who in Arda is called Ilúvatar; and he made first the Ainur, the Holy Ones, that were the offspring of his thought, and they were with him before aught else was made. And he spoke to them, propounding to them themes of music; and they sang before him, and he was glad. But for a long while they sang only each alone, or but few together, while the rest hearkened; for each comprehended only that part of me mind of Ilúvatar from which he came, and in the understanding of their brethren they grew but slowly. Yet ever as they listened they came to deeper understanding, and increased in unison and harmony.

And it came to pass that Ilúvatar called together all the Ainur and declared to them a mighty theme, unfolding to them things greater and more wonderful than he had yet revealed; and the glory of its beginning and the splendour of its end amazed the Ainur, so that they bowed before Ilúvatar and were silent.

Then Ilúvatar said to them: 'Of the theme that I have declared to you, I will now that ye make in harmony together a Great Music. And since I have kindled you with the Flame Imperishable, ye shall show forth your powers in adorning this theme, each with his own thoughts and devices, if he will. But I win sit and hearken, and be glad that through you great beauty has been wakened into song.'

Then the voices of the Ainur, like unto harps and lutes, and pipes and trumpets, and viols and organs, and like unto countless choirs singing with words, began to fashion the theme of Ilúvatar to a great music; and a sound arose of endless interchanging melodies woven in harmony that passed beyond hearing into the depths and into the heights, and the places of the dwelling of Ilúvatar were filled to overflowing, and the music and the echo of the music went out into the Void, and it was not void. Never since have the Ainur made any music like to this music, though it has been said that a greater still shall be made before Ilúvatar by the choirs of the Ainur and the Children of Ilúvatar after the end of days. Then the themes of Ilúvatar shall be played aright, and take Being in the moment of their utterance, for all shall then understand fully his intent in their part, and each shall know the comprehension of each, and Ilúvatar shall give to their thoughts the secret fire, being well pleased.

But now Ilúvatar sat and hearkened, and for a great while it seemed good to him, for in the music there were no flaws. But as the theme progressed, it came into the heart of Melkor to interweave matters of his own imagining that were not in accord with the theme of Ilúvatar, for he sought therein to increase the power and glory of the part assigned to himself. To Melkor among the Ainur had been given the greatest gifts of power and knowledge, and he had a share in all the gifts of his brethren. He had gone often alone into the void places seeking the Imperishable Flame; for desire grew hot within him to bring into Being things of his own, and it seemed to him that Ilúvatar took no thought for the Void, and he was impatient of its emptiness. Yet he found not the Fire, for it is with Ilúvatar. But being alone he had begun to conceive thoughts of his own unlike those of his brethren.