TOLKIEN HAD THE WORDS FOR IT: 13 THE COMING OF THE AINUR

Behold, Iluvatar dwelt alone. Before all things he sang into being the Ainur first, and greatest is their power and glory of all his creatures within the world and without. Thereafter he fashioned them dwellings in the void, and dwelt among them, teaching them all manner of things, and the greatest of these was music.
Now he would speak propounding to them themes of song and joyous hymn, revealing many of the great and wonderful things that he devised ever in his mind and heart, and now they would make music unto him, and the voices of their instruments rise in splendour about his throne.
Upon a time Iluvatar propounded a mighty design of his heart to the Ainur, unfolding a history whose vastness and majesty had never been equalled by aught that he had related before, and the glory of its beginning and the splendour of its end amazed the Ainur, so that they bowed before Iluvatar
and were speechless.

The Book of Lost Tales Part I