Okay, before you play this video, you need to hear the song Hide and Seek by Imogen Heap. You can find it on any mp3 site, and it's most likely on YouTube. In fact...here. I wish I could embed it, but it was disabled.
Now, after you've watched that, watch the video below. There are many awesome a capella groups out there, but of the many that have tried it, only a handful really got it. And these guys are at the top of the list. This is a UNC a capella men's group. (more like Ra capella!)
(rockapella? because they rock? no? okay.)
Ladies and Gentlemen, the Achordants.
There were other groups that came close, like the Dartmouth Dodecaphonics, but none got it just right (the Dartmouth group did it in straight time instead of catching the subtle ritards and accelerandos).
So, you're welcome.