Thanks you 2, I found the answer. Unfortunately, it was not the Void. The answer is.....drum roll please.....The Timeless Halls. Thanks anyhow.
I finally found the source tonight, about two full pages from the end of 'Ainulindal’' at the beginning of The Silmarillion.
But when the Valor entered into E’ they were at first astonished... For the Great Music had been but the growth and flowering of thought in the Timeless Halls, and the Vision only a foreshowing; but now they had entered in at the beginning of Time, and the Valar perceived that the World had been but foreshadowed and foresung, and they must achieve it. So began their great labors in wastes unmeasured and unexplored, and in ages uncounted and forgotten,until in the Deeps of Time and in the midst of the vast halls of E’ there came to be in that hour and that place where was made the habitation of the Children of Il’vatar.
Ooooo! I like that bit.
The Timeless Halls were then, "the places of the dwelling of Il’vatar" and, as it says on the first page of this same source
...were filled to overflowing, and the music and the echo of the music went out into the Void, and it was not void.
This creation story is much more beautiful than that told by Ovid or in the biblical account.
I have now discovered why so many including myself, have missed glombing on to this beautiful piece of prose. We were so enamored with the LOTR,
that when we initially encountered these first pages of the Silmarillion,
we glossed over them because they weren't what we were looking for; they didn't meet our expectations to be 'more of the boys' adventure story'.