The orang-utan's music, if you can call it that, is actually an alarm call known as a "kiss squeak".
"When you're walking the forest and you meet an orang-utan that not habituated to humans, they'll start giving kiss squeaks and breaking branches," says Madeleine Hardus, a primatologist at the University of Utrecht in the Netherlands, who documented the practice among wild apes in Indonesian Borneo.
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