[Legate of Amon Lanc]

Nice topic... let me just say something before we start about things we perceive in the Music...

Originally Posted by spirit_of_fire

When describing the third(?) theme(men), the music was described as the vain, endless braying of trumpets in what was almost a cacaphony, and though the theme did have a kind of rhythm of its own, it seemed that it took the most triumphant notes of the second theme(the elves) and wove it into its own. This might indicate the part the elf friends played in helping the elves stand firm against Morgoth, and maybe they "wove" some of the sorrow into their own theme too, think about Hurin and his sacrifice.

Well... you have the questionmarks there, and rightly so, I think... actually I always understood it the way that Morgoth's music was the vain endless braying of trumpets, and then suddenly the third theme, which was unlike the others - beautiful yet sorrowful - arose, and that was taking the most triumphant notes of Melkor into its own pattern - the sort of parallel to Eru's words:

Originally Posted by Ainulindalë

And thou, Melkor, shalt see that no theme may be played that hath not its uttermost source in me, nor can any alter the music in my despite. For he that attempteth this shall prove but mine instrument in the devising of things more wonderful, which he himself hath not imagined.

I am also not sure about the Second theme being straightaway identified with the Elves. I always thought that the Third theme is the Children of Ilúvatar, altogether: in Ainulindalë, most times the Elves and Men are mentioned only together, as Children of Ilúvatar, which they both are. And later, it is said:

For the Children of Ilúvatar were conceived by him alone; and they came with the third theme, and were not in the theme which Ilúvatar propounded at the beginning, and none of the Ainur had part in their making.

So, of course the sorrow belonged to both Elves and Men. Of course, the sorrows of the world befell them both - as for example your example with Húrin shows.

Speaking of that, I have never been entirely sure about identifying the Second theme with something concrete. There are several possible theories occuring to me right now, not so much specific but rather metaphorical... I think if I was to go with the most basic theory I always had, it was sort of that the original theme was just "unrefined", before the strife between Valar and Melkor changed it - uncorrupted, but still "unproven", too, not enrichened by anything of the Valar's own invention. The second theme, thus, was the way the world was after it came to being, and before there was the third actor - the Children of Ilúvatar - to change it. Sort of 1. Eru (basic idea, which is given forth to be enrichened => attempt to do that => first strife), 2. Valar (the world as it would be without the Children => Melkor still wins) 3. Children (finally the history of Arda as we know it and possibly some eschatological hints about the role of the Children in the battle against Morgoth).