A "100-Voice" Rick Roll
Some guy with way too much time on his hands did a video where he layered 100 vocal tracks of himself singing Rick Astley's "Never Gonna Give You Up". Yes, it's a "100-voice Rick Roll." It's also interesting.
He starts out with four voices layered together and then keeps increasing the layers until he gets to 100. Along the way he does a mouse-like "whistle-tone," opera singers, and even heavy metal screamers.