With these different harmonizers, can one effectively and realistically sound like a backing group.

Example: In The Still of the Night by the Five Satins. Before I come in with the lead vocal, can I cut the "output" of my voice that's feeding into the microphone, so that all I hear is "harmonized" voices without my own voice standing out? Also, can you alternate between original voice and harmonized voice quickly and smoothly (as in the release (bridge) part of the song?