Jazz, with the backbeat of soul music and rock. At it's worst it was a dumbing-down of jazz (like soul jazz' modern-day suit-driven bastard offspring "smooth" jazz), since it relied on the less-complex harmonies and melodies of pop. But its success kept struggling indies like Blue Note Records afloat in the 60's (most releases had at least one "sell out" tune on them), and gave musicians like Herbie Hancock and Freddie Hubbard exposure to a wider, non-jazz, audience.