Sederunt principes

I enjoyed this piece of music, which was written in 1199. I had heard the term "polyphony", and wondered what exactly it meant. Apparently, it just refers to several voices sounding at the same time. Somebody had to do it first, I suppose.

h/t What's Wrong with the World/Steve Burton

PS: I like the reference in the title of the website. It refers to a letter to the editor written by G. K. Chesterton in response to the question, "What is wrong with the world?" His response was:

Dear Sirs,
I am.
Sincerely yours,
G. K. Chesterton