Herbie Hancock covers strikingly varied terrain on his fourth album, a pinnacle of his small-group acoustic period and a tantalizing glimpse of where he was headed. We hear the core of Miles Davis’ groundbreaking quintet—Hancock, bassist Ron Carter, drummer Tony Williams—joining forces with a different trumpeter, the great Freddie Hubbard. “One Finger Snap” became an uptempo test piece for every jazz player, while “Cantaloupe Island,” with its loping funk-jazz, caught the attention of hip-hop nation decades later. “Oliloqui Valley” swings with mystery and restraint, while “The Egg” closes with deep, extended abstraction.