I liked the gentle pop feel of this one. The pitch-shifted vocals worked well, and the light percussion and the little cascading bell-like sound worked very well. I like the way that you spaced the two vocals naturally so that they had that call-and-effect response. A few places, the backing melody you added did not seem to line up as well for me pitch-wise with the two vocal tracks as it did in other places.
Although the creation of a pitch-shifted “second vocalist” is not a new idea, you pull it off with aplomb. I do recommend the original, which is a very nice song indeed. I enjoyed your mix.