9. Al Jackson Jr.
Al Jackson Jr., the session drummer for the legendary soul label Stax, was known as "the Human Timekeeper" until his death in 1975 at the age of 40. During that era, Jackson's distinctively swinging but crisp grooves propelled legendary sides from Wilson Pickett, Otis Redding and Al Green (with whom Jackson co-wrote the hit "Let's Stay Together"); and as his reputation grew, superstars from outside the R&B world like Eric Clapton began demanding Jackson's percussive genius. As a co-founder and key member of Booker T. & the MGs, Jackson's helped pave the rhythmic future for both funk and hip-hop. "I put him in the same bag with Ray Charles or Billy Preston, in a class all his own," Sam & Dave's Sam Moore said of Jackson, who played on chestnuts like "Soul Man" and "Hold On, I'm Coming." "I'll tell it to you straight: He could make shit smell good."