Academy Award-winning sound designer Ben Burtt discusses how he created the voice of WALL-E and M-O and how he came up with the sound and character voice designer for WALL-E.

QUESTION: You had just finished a stint on STAR WARS when you were offered WALL-E and I imagine the last thing you wanted to work on was robots?

BEN BURTT: That is absolutely true. Creating the illusion of voices is the hardest task. It is hard to fool voices. When Andrew pitched this idea and I realized it was all robot voices at first I thought I am sure I have anything left in me -- have I got a new idea, But fortunately it was a very different set of characters. Nevertheless I am sure I approached the same, as I always would have because of my past experience. The idea always is to create the sense of a soul with the character with sound. You are given sounds or a few words and the aim is to create the feeling that these are talking machines. You could have imposed a human voice on to the robots and audiences would have accepted that. But with WALL-E it was important to give the sound an aspect of being a machine. So I went about that task, my assignment was to create voices for the characters and audition them to Andrew. He had about10 minutes of the opening of the movie with sketches and storyboards and said it was a little peek of what he was trying to get. I was there from the beginning, which is the best thing. I am sure that when I started that they did not know that they were going to make his film -- they were still having trials and one of the hurdles to jump was to get the voices.

QUESTION: What was your working process like on Wall-E?

BEN BURTT: A typical day -- I work alone -- I would be in a sound room with my recording gear and mixing consoles, speakers and a screen so that I can project images if I want to. And I really just start improvising. I work two different ways; one is that I have a keyboard and I can put sound effects on that and I can play things. This is how I experiment. I sit alone, I suppose a little bit like musical composition and I try things on the keyboard. I discover a combination and that gives me something to work on. If I need a human input then I can record myself or I can bring in a Pixar employee because they are readily available and free [smiles] for scratch voices. That is kind of what happened with WALL-E. I was just using my own voice as a trial -- I was not supposed to be the voice -- but I was experimenting. Once we got a voice that we liked Andrew realized that it would be pretty hard to go back and start over with a different human voice. So we stuck with it. Plus I was there every day. I auditioned for Andrew many concepts for WALL-E. Some were sound effects because initially we did not know whether he would talk or he might just whistle like R2D2. I think the first version of WALL-E that I did was pretty much like an R2D2 type of character. It was almost with electronic tones. Every time I pitched Andrew an audition he would pick two or three things out that he liked. So I began to make a little list. And then I built up a sort of favorites list.