Bêthberry's post has made my reply quite redundant.
It's true that there's nothing Tolkien-esque about Belle & Sebastian. The Two Towers bit made me laugh, though.
And yes, as regards Sigur Rós, I am chiefly thinking of the albums
() and
Ágætis byrjun. I think the music is quite otherworldly and more beautiful than anything I've ever heard. About the Elvish comment; I'm not actually too fond of the music that the films used for the Elves. I think it's hard to find the criticism, but it seems as though they were trying too hard to 'put it on', if you see what I mean. It seemed a bit fake, just a little bit tiresome. Sigur Ros make me 'see' Elves, whereas the Elves' theme in the movies just makes me think of Liv Tyler.
Ba ba ti ki di do is less Elvish and I have not heard
Von.