Robotic Voice?

Question

How would I go about adding a robotic effect like this to a sound file?

http://youtube.com/watch?v=_NC3Df2J1YU

I'm talking about the green robot's voice, the first voice you hear. Thank you ^_^

Answer 1

This is done with a vocoder. These range from large and expensive to inexpensive. Some synthesisers have one. A software program can also do this using the computer. You use a wav file of the human voice and a wav file of a music sound and the voice changes. Experiment!
Vocoding is described here:
http://en.wikipedia.org/wiki/Vocoder
I include a link to a free software vocoder also.