To appreciate the phenomenon of Astor Piazzolla, a tango innovator of such mythic proportions that he was cursed as "the tango assassin," there is only one place to start: at Zero Hour. Piazzolla wouldn't argue, since he once pronounced the 1986 album "absolutely the greatest record I've made in my entire life." The session -- cut after Piazzolla had spent a decade with his most remarkable ensemble, the New Tango Quintet -- is simply a masterwork in every sense of the term. It was Piazzolla's dream that tango, a dance music born in the bordellos and backstreets of Buenos Aires, could become listener's music, and with a quintet representing a confluence of jazzmen and classically trained players (Pablo Zeigler, Horacio Malvicino Sr., Fernando Suárez Paz, Héctor Console), his dream became reality. Zero Hour exploits their ability to turn from raunchy, crushed velvet heat to cool, artfully poised compositions. Opening with the mantralike voices of the quintet, "Tanguedia III" suggests the aspects of benediction and exorcism to come. "Milonga del Angel" opens with ethereal guitar sketches before settling into a mournful plaint. The highlight, "Contrabajísimo," is by turns bludgeoning and cruel, heartbreakingly sweet, picaresque and cinematic. This is music to get lost in.