Glad you guys liked the article. I particularly liked the points he made about the ancient illustrations of musicians clearly playing harmony; I think even most trained singers would have trouble singing melodies with jumps that big, note to note.

I was also impressed with the illustration of the piper at the bottom of the page, playing two pipes, with two different sets of holes, at the same time.

(and I thought patting your head and rubbing your belly at the same time was hard!) ;-)