She Could Play The Recorder
One of the most impressive tasks that Koko was able to do was playing an instrument. She learned how to play the recorder. Before Koko, experts didn’t think that gorillas could learn such an intricate task.

BBC
BBC
Not only did playing prove that Koko could do something so complex, but it more specifically showed she could regulate her breathing. Wind instruments require the player to release air in a certain way, and Koko was intelligent enough to understand that.