There's something about the simplicity in the high pitched notes that's so relaxing... it's like the charms of Spirited Away are conveyed through that song.
Look up Joe Hisaishi. He's a musical genius and did the soundtracks for all of Miyazaki's films.
Princess Mononoke, besides being considered one of his best films, is his most badass film. If you read the review then you already know it's more adult oriented than his other movies.