My favorite singer. To me, what makes his voice perfect is that it isn’t perfect. That slightly gravelly sound gives it such feeling.
Funny story. He moved into my neighborhood of LA somewhere around 1950 (to the best of my knowledge as I wasn’t alive at the time), and it caused quite a stir since at the time the neighborhood was all white. Some of the neighbors raised quite a stink with one confronting him by saying something to the effect:
“We don’t want any undesirable people around here.”
Nat’s response (paraphrased)?
“You know, I don’t either. If I see any, I’ll be the first to let you know.”
His voice was chemically enhanced.
Before a session he would smoke a half pack of cigarettes to give his voice "tooth" which is that gravelly effect you mention. Not surprisingly, he died of lung cancer.