One has to learn how to use a vocal harmonizer correctly and how to sing using them.
One of the things that happens allot is that if you mic picks up the sound of the keyboard from your speakers, then you will also get the keyboard sound harmonized too and it comes out a mess.
You need to have your speakers etup, so the mic doesn't pick them up. To experiment and see if this is part of the problem, tuen off your speakers and try using headphones and see what you get.
You also have to experiment with the different harmony effects as to how loud you sing and how close or far away from the mic you get. All of that makes a difference.