Jazz's history of fusion with R&B is rooted in this keyboardist's pioneering use of the Hammond organ. By the mid '50s, his unique range of languid swing and hard groove—perfected on albums for Blue Note—helped jazz stay on the pop charts, while also providing new approaches to improvisation that would inspire successive generations of jazz explorers. He worked in small combos, but also brought his fast flurries of notes to snazzy big band arrangements (as on the album The Cat). And his collaborations with guitarists like Wes Montgomery and Kenny Burrell are also cornerstones of his catalog.