Despite the influence that acting technique may or may not have had on his style of singing, we must not forget the influence that the classic Italian Bel Canto singing tradition most likely had on him. After all, he was a first-generation Italian-American. Opera still had to be in the blood of his parents, as it was for all Italians in the first years of 20th century. It’s likely that Sinatra, being the fervent music enthusiast that he was, either consciously or subliminally, imbibed aspects of that tradition.
Beyond that, he received vocal instruction and guidance off and on throughout his career. Vocal instruction then as now, at least in principle, has always tried to teach Italian principles of beautiful singing. So we have to concede that there was a connection—however weak or strong—to his parent’s country land. Still, we need to be careful not to take this relationship to Italian origins too far: for all the Italianate qualities in his singing, and for all the influence that Italian singing tradition may have had on him, his art was, nevertheless, perfectly wedded to the popular American music traditions of the first half of 20th century.
Artists like Benny Goodman, Tommy Dorsey, Bing Crosby, Louis Armstrong, Mabel Mercer, and Billie Holiday initiated early jazz and swing traditions. Sinatra was especially enamored with Crosby whom he idolized. At the very beginning of his career, in fact, he not only was a devotee of Crosby’s singing and vocal sound, but even took on some of Crosby’s dressing habits (e.g., he wore a Crosby-like hat his whole career). Sinatra, who was committed to being the best singer he could be, ingested, synthesized, and advanced the innovations of the pioneers of jazz and swing.
As a tireless student of his art, he learned from their passions (Armstrong), rhythms (Goodman), lyrical honesty (Holiday), narrative style (Mercer), legato phrasing (Dorsey), and naturalness (Crosby). From this vantage point, we could say with confidence this much: Sinatra's unique brilliance existed in his ability to create a new vocal sound—and a new way of singing—by integrating into a seamless whole the classic Italian ideals of beautiful singing, the early American 20th century jazz/swing traditions, and his own innovative word melody style.
Image source: William P. Gottlieb/Wikipedia