 David Crosby, a singer-songwriter who helped define the sound of the Woodstock generation as a key member of the 1960s and 70s bands the Byrds and Crosby, Stills Nash, but whose wanton drug abuse made him a cautionary symbol of the eras culture of excess, has died at 81. A former publicist, citing family ... David Crosby, who embodied the Woodstock generation, dies at 81... 