BIRTH OF THE BLUES: As a child, Jeff Lambert (Bing Crosby) hangs out in New Orleans' Basin Street, playing hot swing on his clarinet instead of the classics his father prefers. He's Inspired by an African-American group there and some years later, at the turn of the century, sets out to form a jazz band of his own. With cornetist Memphis (Brian Donlevy), singer Betty Lou Cobb (Mary Martin) and trombonist Jack Teagarden (Of the Original Dixieland Jazz Group, after which the story is patterned), he's on his way. A veritable history of jazz follows. From jump and jive to sweet romanticism, half a century of popular hits is given spectacular treatment. "By the Light of the Silvery Moon" is sung in a theatre with lantern slides on the screen. Singer Ruby Elzy's "St. Louis Blues" is backed by a chorus of eighty. And "Wait Till The Sun Shines, Nellie" brings Crosby and Martin together in a knockout duet.