You might notice that Jazz singers often have a CONVERSATIONAL approach to their phrasing. This is a great starting point when learning to sing Jazz. Listen to the endless list of great Jazz artists (Louis Armstrong, Ella Fitzgerald, Tony Bennett, etc.) and you'll notice "speech-like" tone accompanied by inflections, pauses, emphases that are very specific to each singers' conversational style. In Jazz, individuality, improvisation, and originality are favored over replicating every written note and rhythm. Learn the original music first as a road map. From there, you can begin to improvise notes and rhythms via your own conversational instincts. Ultimately, your improvisational choices should feel very similar to having a lively conversation on pitch!