Before Miles nailed down the lineup of his second great quintet, he experimented with different saxophonists, and this set offers a rare look at his partnership with Sam Rivers. On “If I Were a Bell,” the tenor player’s style includes some overblown textures while he pushes the band into avant-garde realms; drummer Tony Williams sounds ready to join Rivers, but the trumpeter is more restrained. The slightly uneasy fit makes for thrilling listening, as the players negotiate a rich variety of creative possibilities.