Mellotronists

Jon Anderson used some interesting new technologies during his one man
show "tour of the universe" this fall.

http://www.jonanderson.com/

He used TC Helicon's VoiceLive processor to create vocal harmonies. 
This processor is a digital pitch shifter that generates up to four
part harmonies.  It is also a pitch correction processor.  (We know
Jon could use that live).

http://www.tc-helicon.tc/VoiceLive

He decided NOT to use a midi sequencer to control the VoiceLive
processor.  He used a midi-equipped acoustic guitar.

I am just guessing, but I would think that the midi guitar could cue
the processor re: the key and tempo.  Other stuff?

Clay