Writing about Louis Armstrong in the NYTimes, Joe Nocera observes:
Starting in the mid-1950s, the State Department began sending jazz musicians like Dizzy Gillespie, Dave Brubeck, Duke Ellington, and Armstrong on tours abroad as good-will ambassadors. Part of the rationale was that jazz was a uniquely American art form that could show off the best of American culture, just as the Russians used ballet troupes to show off their culture. The government also thought that these artists, most of them black, might, by their presence, help diffuse “the widely shared sense that race was America’s Achilles’ heel internationally,” as Penny M. Von Eschen writes in “Satchmo Blows Up the World,” her book about the jazz tours.The State Department sent the musicians to Cold War hot spots all over the world. Everywhere they went, their music was received enthusiastically. It was great music, to be sure, but it also often represented “things that were culturally forbidden” in repressive regimes, says Dan Morgenstern, the jazz historian. At the height of the jazz tours, The New Yorker ran a cartoon showing a State Department meeting: “This is a diplomatic mission of the utmost delicacy,” the caption read. “The question is, who’s the best man for it — John Foster Dulles or Satchmo?” Dave Brubeck and his wife, Iola, even wrote a musical celebrating Armstrong’s international forays, called “The Real Ambassadors.”
Nocera's piece specifically centers on a tour that Armstrong took behind the Iron Curtain (i.e. the Soviet bloc) in 1965. During that tour he restored a tune to his repertoire that he hadn't otherwise performed in a decade. The tune was Fats Waller's “(What Did I Do to Be So) Black and Blue?” The title says it all:"... he played it on every stop during his Iron Curtain tour. He also played it slower than he ever had, so that it became a mournful lament."