“A favorite of audiences thanks to his alluring voice and heartthrob presence, Mr. Hvorostovsky cut a striking figure, his trim 6-foot-1 frame topped by a mane of prematurely white hair. He also had a compelling personal story: He escaped the street-gang life as a teenager in a grim Siberian city, found his talent there despite the region’s cultural isolation, and overcame a tempestuous drinking problem that could have ruined his career.”