I've tried it using Waves Doubler and their ultra pitch without much luck. I put the 4 band members in my big room with a U87 on Omni across the room and had them do the parts(screams) many times, then I used most of them and panned them differently across the stereo field appropriately so they fit in with the instruments....awesome.....sometimes there's nothing quite like the real thing.
Sorry I didn't have the answer you were looking for, but hope this helps
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