I was watching on In rainbows From the Basement VH1's site. On the song "Nude," you hear this synth thing going on (like a pad), but I'm pretty sure it was a guitar. It wasn't your usual suspect synth sound (crystals, shimmer, etc). It seems like 100% wet verb and some pitch shifting, but does any body know specifically? Here is a link to the video, it's not the first one that plays, I think it's #2, again on nude.