In the spring of 1947 trumpeter Louis Armstrong was 45 years old-considered by some critics and fans to be all but washed up, with his best years behind him and his music made irrelevant by the rising force of bebop. For 20 years he had been one of jazz's leading, most influential figures. He was appearing in a new movie, set in his native New Orleans, and he remained a popular artist. But he was facing some daunting challenges as commercial and aesthetic styles in music began to change rapidly in the years following the end of World War II.

A concert at New York City's Town Hall in May of 1947 came to be seen as a turning point for Armstrong. Placing him in the company of sympathetic musicians such as trumpeter Bobby Hackett and trombonist/singer Jack Teagarden, it opened one of the most interesting stretches of Armstrong's career-a ten-year period that would find him hitting the charts with pop ballads, forming the small-group All-Stars that would sustain him as a live performer for years, and becoming a symbolic ambassador of jazz for the United States during the Cold War.

Jazz writer Dan Morgenstern and historian Michael McGerr join us on this episode of Night Lights with insights into Armstrong's relationship with young bebop musicians, his success with lushly-orchestrated pop ballads made for the Decca label, his move to the small-group format, and his significance in the culture of the Cold War and the growing civil-rights movement of the 1950s.