I think reatune uses pitch correction too, that's why. In reapitch you tell the algorithm to go 2 semi-tones lower for exemple, in reatune you tell it to adjust to pitch to play a specific note. I didn't play with the differents algorithms in Reatune, but in reapitch, for differente type of sources (voices, guitars), some algorithms give best results than others, and for some I hear no differences.