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iPi doesn't do key reduction on its own.
You could manually use takes to reduce keys somewhat in iPi, (but not best approach), if you wanted to blend the takes in MoBu or other 3D editors.
It isn't good practice to use auto-key reduction in 3D editors, and depends on the editing program, what curve/graph editors it displays and options it has.
If you are talking about using a form of pose to pose reduction in Motion Builder, you can do that also by choosing key pose frames (by adding a separate Character Animation Track in Story Mode first), so you can reset keys and plot to skeleton as a reduced key animation. (You would need to play with tween frames to get better transitions this way).
Down and dirty video tutorial on this option:
http://vimeo.com/82895521