Yeah, good ones slaw---Little Richard!---(and everyone else). Ray Charles has to be the most influential of them all---Steve Winwood, Richard Manuel, Van Morrison, so many others citing Ray as their model. Big Joe Turner is a favorite of mine, as well as Howlin’ Wolf, THE blues singer. Tom Waits is about as unique a voice as I know of, and let’s not forget Otis Redding and Sam Cooke. For Rock 'n' Roll, Chuck Berry's lyrical/vocal rhythms are one of the very pillars of the music.
From the gals, Aretha Franklin is at the top of the list. So are Big Mama Thornton (Elvis copied her recording of "Hound Dog"), Brenda Lee, Loretta Lynn, and a favorite of mine, Tammy Wynette. In the modern era, Chrissie Hynde (The Pretenders) is immediately recognizable.