The Lord of the Rings: The Fellowship of the Ring, Extended Edition - The Appendices, Part Two: Well, I'm finally through the appendices. What a fantastic package they put together. Some of my favourite stuff was on the soundtrack and the score. Apparently the sound guys were having a hell of a time with the Ringwraiths; they couldn't produce anything bone-chilling enough. So during one of Peter's visits, they play what they have for him, talking vaguely about what they were really aiming for. Just like that, Peter says, "Fran can scream like that." (Fran is Peter's wife, involved in all the writing, co-author of the script, you name it.)
Hours later, Fran "knocked the sound guys on their asses" (their words) with these horrid, banshee-like screams. That's pretty much what you're hearing on the soundtrack: a woman's scream. I'm glad my wife doesn't scream like that. *shudder*