from The Letters of J. R. R. Tolkien, continuation of a draft letter to Ms. Rhona Beare, 14 October 1958
When
the One (the Teller) said Let it Be, then the Tale became History, on the same plane as the hearers; and these could, if they desired, enter into it. Many of the Ainur did enter into it, and must bide in it till the End, being involved in Time, the series of
events that complete it. These were the Valar, and their lesser attendants. They were those who had 'fallen in love' with the vision, and no doubt, were those who had played the most 'sub-creative' (or as we might say 'artistic') part in the Music.
It was because of their love of Eä, and because of the pan they had played in its making, that they wished to, and could, incarnate themselves in visible physical forms, though these were comparable to our clothes (in so far as our clothes are a personal expression) not to our bodies. Their forms were thus expressions of their persons, powers, and loves...