"Embraceable You." "Someone to Watch Over Me." "Alexander's Ragtime Band." "My Funny Valentine." "White Christmas." Irving Berlin once wrote a song entitled "The Song is Ended, But the Melody Lingers On," and surely the title is a perfect epitaph for an incomparable era of American songwriting that endowed us with so many of our most beloved ballads and rousing showstoppers. The Song is Ended is the story of the Golden Age of American popular...