John Stefan, I think you misapprehend the
Music of the Ainur (in
Quenya, the
Ainulindalë, literally “Song of the
Ainur”). The Music was set forth by
Eru, and the Ainur sang before him as he directed them, adding their own peculiar touches to the theme he proposed to make it ever more beautiful. But
Melkor decided he wanted another theme, one of his
own devising, but not so much a “theme” as a cacophony, a repetitive noise that distracted the others following Eru’s lead. So Eru began a second theme, and Melkor and the Ainur who followed his lead disrupted this as well. Eru finally had enough of Melkor’s shenanigans, and ended the Music himself with a great chord the like of which none of the Ainur had ever imagined. Then Eru spoke the Music into physical form,
Eä!, “Be!” And many of the Ainur,
Valar (greater) and
Maiar (lesser), took on physical form and entered into the physical manifestation of the Music. The First Theme of the Music was revealed in the world,
Arda, as the
Elves; the Second Theme as
Men, who came later. The Valar did not create either theme, as they did not create either Elves or Men, the Children of
Ilúvatar (Eru: “Ilúvatar” is Quenya, “Eru”
Sindarin), nor did they need to “begin the Second Theme:” the time of the Music, of the Ainulindalë, had already passed: they were
living the Music they had sung before the creation of physical stuff, of Eä. Their prescience (seeming foreknowledge) of
events in Eä (creation, the universe), and in Arda (the world) specifically, was predicated (based) upon their understanding and comprehension of the Music they had sung and heard before the physical world came into existence.
This tale reflects the Christian view of creation, and specifically the Roman Catholic view of the fall of the angels. It isn’t exactly the same: it’s just a
reflection, a model or similar tale, to what
Tolkien – and many of the
authors and works he studied both professionally and personally – believed. It is similar to traditional Judeo-Christian
cosmology.
God creates the angels, and they sing before him; then (in Catholic theology) he creates the physical universe – remember, the angels are
spirits, intellects without bodies or physical forms – and proposes to enter into it himself as a mortal man (this is very Catholic!), at which point Lucifer, the greatest of the angels,
objects and many others follow his lead: “I will not serve!” meaning that they, as powerful, immortal spiritual beings refused to help these puny mortal
creatures of flesh and blood and few and finite days upon the earth. The angels who rebelled made war upon the angels who remained faithful, lost, and were cast out of God’s presence, out of heaven, and since then have been scheming and plotting to twist and destroy as many men and women as they can. That’s the story that is being
reflected in Ainulindalë, or at least a large part of it. And the Christian hope of redemption is further reflected in the “Old Hope” that appears in “The Debate of
Finrod and Andreth” in
Morgoth’s Ring, when Andreth in her despair reveals to Finrod, her estranged lover’s brother, that some Men held to the “Old Hope” that Eru himself would enter into Arda and heal the marring caused by Morgoth and his minions.
But the Valar could not “start the second music of the Ainur;” the Second Theme had already taken place before there was any Arda (the world), before Eä (the universe), before the Ainur ever imagined that such things could even be. The First Theme, the Elves, existed for time uncounted beneath the stars, before the sun or moon. (Hence the “Eldar”, the “People of the Stars”.) The Second Theme, Men, arrived just as the Eldar first began to fade. The Elves had many names for Men, calling them the
Atani, the “Second People” (in Sindarin,
Edain, as in
Dúnedain: “West Men”,
Númenóreans); the
Hildor, the “Followers”;
Apanónar, “Afterborn”; Engwar, the “Sickly” (Elves were not susceptible to illness, though they might starve (long after Men would be dead from such starvation) or die of thirst (again, long after Men would in similar circumstances), of wounds (the fate of most of the
Noldor who rebelled, following
Fëanor to
Middle-earth), and of grief or despair); and the
Fírimar, the “Mortals,” for to the shock and grief of the Eldar, Men were short-lived and soon died, passing out of Arda altogether to some destination of which the Elves knew nothing: This they called the
Gift of Men: for the Elves could
never leave Arda, lingering in regret and sadness through all the
ages until the end of the world. (Men saw their Gift quite differently!)
If you’d like to push this analogy just a bit further, the mixing of the First and Second Themes, of Elves and Men in Middle-earth, is similar to the mixing of the living Light of the Two
Trees, Telperion and Laurelin, that Fëanor caught in
the Silmarils.