Gorillas Have Individual Tastes in Music

This could explain a lot when it comes to humans. It turns out that gorillas are music fans with tastes as individual as yours. From Discover Magazine:

Problem: you have a bunch of gorillas coming over for a party and you have no idea what music they like. Solution: apparently there is none. That’s because, at least according to this study, gorillas have individual responses to different kinds of music. Here, researchers observed three gorillas (Koga, Sydney, and Lily) listening to rainforest sounds (natural), Chopin (classical), or Muse (rock). Although all the gorillas changed behaviors when listening to the rainforest sounds, Koga oriented toward the speakers playing Muse 40% of the time, while Sydney did it 10%, and Lily never did (graph below).

Question: Why did the researchers not go with, you know, Gorillaz? Or was that too obvious?