Neil,
At first, I was just being lazy. It is past my bedtime and I should get up early tomorrow. They are calling for snow in the AM and it makes commutes treacherous (and mine is 35 miles one way).
I decided not to go to bed stupid, however. A quick (and I do mean quick0 search got me the following site. CLICK HERE to read up on Tuvan overtones.
The nice thing is, I didn't lie very much in my previous posting. By the way, I should credit Anne Hills for the information I gave. She can do a double overtone.
Roger in Baltimore