#1
What's a good vocoder to make the voice robotic and modulated, not a vocoder that actually makes chords depending on your pitch.

Example: Kid A
DEAD. AIR. SPACE.

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#2
The only one i've used is the one you get in reason. Which is a pretty descent vocoder.

And i think pretty much all vocoders work the same way. They use the pitch from one instrument to modulate the pitch of another instrument.
So if you chose the input as your voice and for the output you use a "robotic" sounding synth, you should be able to make your voice sound robotic...