Cannibal Holocaust Main Theme

So I'm way too much of a pussy to actually watch the movie, but I've always assumed it was a depraved, gory, shock value-driven, schlock fest and nothing more. That is, until the film's main theme automatically came on my Spotify. It's so beautiful pleasant and haunting, I was so curious what it was from and you can imagine my shock when I found out. Now I'm just really curious what the overall tone of the movie is? Does the beautiful music match the contents of the film or contrast it?