He was in a period of his artistic life in which any song he sang would have distorted it and made it so beautiful that it would no longer be sung and interpreted by any other singer, unless he wanted to make a fool of himself.
I really wish Frank Sinatra and sung some duets with Ray Charles during the sixties and seventies. Those performances could have easily have been as magical as his collaborations with Jobim.
I don't think you're implying this, but just in case, know that Sinatra was always a big proponent of Civil Rights and a major ally of the NAACP. I know some people see Sinatra and think "he's old so he's racist", but ofc his performances of Old Man River were sung with knowledge and intention.
