You're obviously far more musically attuned than myself. On a personal level I'm far more drawn to Luther's voice than Celine Dion but that may be just more about musical style than ability.His accuracy was what put me off his voice. I do piano tuning, many singers can do this...in the middle of my range I sing pitch perfect, but if I go lower I flatten the notes accordingly, and if higher I gradually sharpen the notes. Celine Dion and Steve Perry are fine exponents of this craft...it gets to the soul and is often the difference between a singer and a performer.