I found a link to this clip describing the "Waves of Sorrow" song over on Eric's blog (thanks Eric!). Very cool stuff about a soon to release "The Joshua Tree Demos" over on the U2 website.

(Clip removed as I found it too annoying that it auto-played. Go over and watch it on the U2 website if you are interested. It's fun to watch Bono discuss the song, the impressions made during a trip to Ethiopia and seeing him sing along with himself as the recording is played.)