Mal Waldron was the ultimate singer's pianist, providing the kind of delicate, atmospheric backdrop that allowed frontwomen like Lady Day to tear into their songs with stunning emotion (his version of “Willow Weep for Me” with Holiday is a must-hear). But he was also a musician's musician, gleefully poking holes in jazz convention with fellow mavericks such as Eric Dolphy on serpentine tracks like “Fire Waltz.”