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.
Musically it reminds me of the thing on the left (which Kirby sent to me—thanks!) and visually, like the horses on the right, photographed at a roadside stop in northern Minnesota in 2007. Below those, just to make a richer set, are Bobby McFerrin on the left and 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).
Since then, the easiest access to fancy polyphany is probably Pentatonix. They have a Youtube Channel, and all their stuff is great: