One of my contemporaries - Johnny Mathis - is still performing, altho he now limits his public appearances to 50 or 60 concerts a year. That's still a bunch!
I cannot imagine "Silver Bells" sung more beautifully than by Johnny Mathis. The crystal clear clarity of his velvety voice can be easily heard in this clip.
Wiki has an extensive writeup about him if you'd like to read more, including some little tidbits that I didn't know about, such as his prowess in sports and his operatic training.