The trumpeter’s second great quintet created an exalted sense of mystery on this 1968 recording. During the title track, the melody loops around and around, suggesting infinity—but as drummer Tony Williams muscles in some frenzied rhythmic variations, it takes on a new life. Hard-bopping tracks like “Madness” and “Riot” (written by pianist Herbie Hancock) provide brisk energy, but the album’s secret weapon is the group’s ability to weave in and out of the themes.