I think it comes down to a matter of balance between emotion and technique. People talk about a singer like George Jones having a four octave range but when you listen to him, and tune in to the pure emotionality of it, who gives a shit about the technique. It's there, but unstudied and purely natural. Other singers that might fall under this rubric would be Robert Johnson, Hank Williams, Howlin' Wolf, Billie Holiday, Otis Redding, Sandy Denny, to name just a few that come to mind. All of which seem to possess a natural gift that others then later try to emulate by imitation and/or training with variable levels of success.