Perpetuum Jazzile performs "Africa"

I noticed this video was posted on several websites this past week, but I was in a hurry and didn't click it. Today it was emailed to me by a friend whose opinions I value, and I'm glad now to have watched/heard it.

The featured song is "Africa," a chart-topper from the early 1980s by Toto. The performers are Perpetuum Jazzile, an a capella jazz choir from Slovenia. What impressed me about the video was not the song itself, but rather the 2-minute introduction during which the choir produces the sounds of a gentle rain in Africa escalating into a thunderstorm.

I suggest starting the video, then looking elsewhere (down this page, or open another tab for browsing) so you can hear the sound effects (note - no instrumental or percussion help). You'll probably then go back to see how it was done.