I must get one of these things:

The harmony processor creates 2- to 4-part harmonies directly from your vocals, in the same key as your accompanying instrument. Studio-quality reverb lets you independently add depth to your dry and harmony vocals.

The focused 256-band articulate vocoder, designed by the same EMS genius who made vocoding famous, features adjustable harmonic enhancement and controllable formant shift.

Demo (the guitar bit comes roughly 2 minutes in):

Not a bad tune, either!