Reading LOTR again after the Silmarillion and noticed a few more things with regard to music I didn’t remember from way back when I read it the first time (also forgot how different the books are from the movies, but it was a long time ago when I read the books):
First, beside the music of the Ainur creating history, Tolkien gives music a dominant role in another sense: when the hobbits meet Bombadil, one of the oldest entities in middle-earth if I understand it correctly, he uses music to exercise his power over living things in his region such as the big bad old tree that is trying to capture the hobbits.
Second, every few pages in LOTR there is another song… These are very often based on ancient stories that are also included in the Silmarillion and sometimes completely written in one of the languages he invented.
So music was not only a powerful world-creating and world-shaping force in the world Tolkien created, but also an important way for Tolkien in his writing to give a deeper background to his story without diverging to much from his main storytelling. It is interesting to see how important music was for Tolkien’s work in multiple ways.
[Edit:] Even though I like the movies, these thoughts and all the stuff excluded from the movies kinda make me wish there was another movie adaptation with more sense for the music and storytelling aspects and less focus on fighting and war…