An explosive memo concerning leaders of the famed Boys Choir of Harlem and how they handled a case of abuse against one of the choir’s boys, threatens to result in the ouster of the choir’s founder. “The accusations against the Turnbulls have dealt the choir and its academy a painful blow at a time when both are struggling with their finances, as they have on and off for many years. The crisis could signify the end of an era for the group, which has performed from Yankee Stadium to Tokyo, and the beginning of a decidedly shaky future.”