Here's a really good recording of Water Night
http://www.youtube.com/watch?v=2pg0tuah-VAAnd here's a really haunting song from an Australian composer. My senior year of high school we did this at our last concert... I got to do some of the overtones at the end.
http://www.youtube.com/watch?v=ooNvbg4dKNMListen carefully.. you can hear overtones throughout the song... this is an impeccable performance of the song. The overtones are the fluty sounding noises that sound like they're higher than anything the rest of the choir is singing. Buddhist monks do it a lot.