It was for stage bands, for dancing, and for a jiving mood of letting go. Throughout the nation swing re-sounded with the spirit of good times. But this pop genre, for a decade America's favorite, arose during the worst of times, the Great Depression. From its peak in the 1930s until bebop, r & b, and country swamped it after World War II, swing defined an American generation and measured America's musical heartbeat. In its heyday swing reached a mass audience of very disparate individuals and united them. They perceived in the tempers and tempos of swing the very definition of modernity. A su