This one is hard to get right. Turn horses on and off by clicking them on (and maybe off again until it comes around for another shot) until their little Swedish doo-wop is synchronized.
Rockapella playing sing-off with True Image from "Spike Lee Does it ACapella, from the 1980's (with Spike Lee and Debbie Allen goofing around on the side there).
Bobby McFerrin:
Since then, the easiest access to fancy polyphany is probably Pentatonix. They have a Youtube Channel, and all their stuff is great:
