Good example, @orpheus10. Ray is imo the most important and influential male singer of 20th Century Pop music (along with Hank Williams). Does that sound too "grand"? ;-)
And I consider Big Joe Turner perhaps the first Rock 'n' Roll singer. He too straddled the line separating Blues and Jazz, coming from the Kansas City Jazz scene, but recording the original version of "Shake, Rattle, & Roll" (covered by Bill Haley for the white market). I came to love Joe when I discovered the whole Jump Blues scene of the late-40's/early-50's. Great, great stuff.