Jazz has always included improvisation, but since the 1950s some jazz musicians began to improvise outside traditional structures of melody and harmony—and after all those decades, the music that results remains challenging. Saxophonist Oliver Lake and drummer Barry Altschul were already in the caravan as jazz ventured off into the unknown. They are still at it in the OGJB Quartet, a combo with two younger musicians, cornetist Graham Haynes and bassist Joe Fonda. The woodwinds circle and intersect meaningfully, suggesting melodies beyond the normal range as Fonda lays down a rhythmic thrum and Altschul tackles the beat from the left-hand side. With its African influences, Bamako should appeal to devotees of Lake’s earlier ensemble, the World Saxophone Quartet.