Then I heard him sing a few songs live into a mike in front of an actual orchestra. His voice was like an instrument, the dominant instrument, of the orchestra. Not a separate thing but the essential element. I have heard nothing like that from any singer before or since.
A lot of people don't get that there are several phases to Sinatra's singing career. All are so different thay almost sound like a different person. There's the young crooner who was the idol of bobby-soxers, then the swinging bachelor guy of the 50's in a fedora (the Capitol Years - his best years IMO), then the Rat Pack years of the 60's, followed by his years of touring in a tux from the mid-70's to his death. Most non-Sinatra fans probably think of "New York, New York" when they think of Sinatra. That was basically his last big hit, and done after his voice had lost much of its range and elasticity.