I'm writing these words exactly 100 years after the day that Francis Albert "Frank" Sinatra was born. A lot has happened musically since then, but Sinatra and his music continue to inspire musicians of all ages and styles. (Ballplayers too, judging from the sounds of "New York, New York" I hear whenever I go to nearby Yankee Stadium.)
Sinatra had many sides, musical and otherwise. He could "sing it pretty," move you to tears with a torch song, and swing his rear-end off when he wanted to. It's not for nothing that famous jazz musicians voted Frank their favorite male vocalist in a 1950s Downbeat magazine poll. (Think about this for a moment: with all the great jazz singers out there, the jazz instrumentalists voted for Sinatra, a non-jazz singer!)
Here's why jazz musicians like him so much: Even though Sinatra was more of a pop singer of his day than a straight-ahead jazzer, he sang with a jazz musician's rhythmic feel. He swung!!! In fact, the biggest lesson I ever had about Sinatra's sense of swing occurred when I was conducting a concert of Sinatra's music featuring a large orchestra and a male vocalist. Even though the orchestra consisted of New York City's best jazz and session musicians, something was missing. Something intangible.
I spent the entire rehearsal process trying to figure out what exactly was missing, and then halfway through the concert it hit me: Sinatra had such a strong sense of "swing" that even the best jazz players on the planet had to keep up with him. On songs like "The Summer Wind" and "Fly Me To The Moon" he pulled them along!
Usually it's the other way around: the band swings hard and propels the vocalist. Instead, Frank inspired his "accompanists" to swing harder than they usually did. On his terms.
Have a listen to The Summer Wind to hear how hard Frank Sinatra swung. (He starts out by singing lyrically, then check out how he digs in at 1:09). Try to bring some of this into your own jazz playing and notice how well the audience and your fellow musicians respond.
If you want to become fluent at improvising over jazz standards, check out my jazz piano video course. I've designed it so you learn to apply the theory at the same time you learn it, at every step of the way!