Against lush strings or jumpy jazz, Lady Day always holds sway. This cross section of various eras finds her both tenderly romantic (“Softly,” “For Heaven's Sake”) and surprisingly playful (“Jeepers Creepers”). But while her backing and mood can change drastically from song to song, the constant is a mesmerizing delivery; she drops jaws to the floor amid the slowly expanding heartache of “I Cover the Waterfront.”