I've enjoyed reading this thread. I wonder if one can differentiate between a jazz singer and a "jazzy" singer. Frank could swing--and does on that cool version of "Serenade in Blue," but if you then listen to Stan Getz's version of the same song from his Cool Sounds record, you see how a real jazz artist does it. As much as I love Sinatra (and I *really* love Sinatra's music), I've never been able to see him as a jazz singer, per se. I think improvisation really is the soul of jazz, and while Frank occasionally embellished a song--especially singing live--he didn't improvise much.