Re: Vai Recorded Harmonies
I don't know how Vai (specifically) records his harmonies, however there are ways of telling whether or not a harmony was generated by a harmonizer. Harmonizers will generally generate harmonies that are a consitent specific interval from the melody line (as chosen by the player/program). Thus if you hear a harmony that is consistently the same interval (say, a minor 3rd above) throughout the run, it is most likely a harmonizer. If, on the other hand, you hear a harmony that uses different intervals during the run, it is more likely that it was actually played rather than program generated. Also listen for subtle playing differences in the harmony such as note duration differences, slight bends or vibrato, etc. These are also great indications the harmony line you are listening to was actually specifically written and played and not just digitally generated.