Eclipse can provide up to 8 parts pitch shifting. Chromatic/Diatonic/Reverse are the main flavors. As for any pitch shifter, the more you raise/lower pitch away from 1/3rd of the main freq of a sound source, the more artifacts you may get. It's just the nature of it. In this case a bit of eq and a back positioning in the mix helps a lot, still providing harmony though.
all the best