"As Cunningham explained, he has been recording train sounds from outside his U.K. apartment for ten years, and for this piece he replaced 90% of the Scott-Heron’s musical track with these train sounds and environmental recordings, pitch-shifting and harmonizing them to create a “musique concrete” version of the original composition"
Here is an article to tell you all about it. It's good to hear that Chris is using his considerable talents to bring us music as well as video nowadays, look forward to hearing more . . .
Here's a one screen version of what he premiered (the original had three), it's awesome. At the time of writing, it's taking ages to play so you might want to give it a while to load if you can't be arsed with the stuttering . . .
http://www.theonion.com/articles/yes-sweetie-mommys-heard-of-gil-scottheron,11141/