It's the elvish singing part in FotR for me, The Passing of the Elves I think it's called. I always thought, while reading the book before the movies, that the song A Elbereth Gilthoniel is a sad but terribly beautiful song, with the Elves' choir-like voices and harps and stuff. Not violins or pianos like the other classics, but something like Gregorian chant but with female voices included.
