Edit: I take it back, partly--this first one isn't as dead on a match as I first thought. It's only kinda cool, like a similar key change.
Got a way to play two songs at once? Try it with "Sometimes You Can't Make It on Your Own" (How to Dismantle an Atomic Bomb) and "Mothers of the Disappeared" (Joshua Tree). Sync 'em up so they both hit the key change at the beginning of the chorus (at 1:00 on "Sometimes" and at 2:05 on "Mothers") at the same time. They're the same musical idea in the same key, reworked by the same band nearly twenty years apart. The rest of the chorus on "Sometimes" ("And it's you when I look in the mirror") plays like an almost spiritual upgrade on "Mothers," with more hope written into the music and the lyrics. A cool glimpse into U2's musical evolution.
Edit: but this second one is solid.
Want to hear a very bald example of sampling? Play Craig David's "I'm Walking Away" before or after U2's "One." The entire song is Edge's guitar riff from the opening bars. Same key, same tempo.
(x-posted to my journal)