Ben Burtt created some of the most memorable sounds in the Star Wars world, including the blasters, Darth Vader’s breathing, and Chewbacca’s voice. In this interview, Burtt discusses what it was like to create the most difficult voice he had to create: the bleeps and bloops of R2-D2.

Burtt experimented with a lot of machine sounds to create what might come out of a computer, for example. But he found that was too machine-like and R2 was more than just a machine in the films. He ended up thinking of the sounds a baby might make trying to communicate and combined those sounds which Burtt made with his own voice with electronic sounds via a keyboard.