Folks which of the following arrangers would you say has the best built-in vocalizer?
Korg Pa800
Korg Pa900
Yamaha Tyros 4
Yamaha PSR-S950

I know VoiceLive makes a variety of stand-alone vocal harmony units. But one of the features that's most important to me is a subtle pitch correction. Without experience, I'm guessing that feature would be more reliable on a built-in unit that has direct access to the arranger's chords.

Please educate me on this issue and offer your recommendation. Thanks!