Polyzony

Georgian folk music has been designated by the United Nations as a masterpiece of humanity's international heritage. It's also incredibly fun and tonally pitch-bending to sing. If you want to hear and learn more, visit

http://www.polyphony.ge/en/homepage/home.php

(where you can search for mp3's of folksongs by style, region, type of accompaniment, and other criteria)

and

http://www.angelfire.com/ga/Georgian/music.html

(for a historical overview of unguaranteed veracity.)