Kyrie Eleison

Silly event of the week : I was sitting in my room and I heard someone outside on the street whistle a vaguely familiar melody. At first I couldn't place it, but suddenly it got to me : some kind of freak was happily whistling a Gregorian 'Kyrie'... while walking down the street. That's why it was so difficult to place. I only know that melody from a couple of masses I had to attend with the choir I'm singing in : a rather different setting. Anyway, I've posted along the sheet music of the part he was whistling, in Gregorian notation of course.