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.”

The second subplot involved timing: The East Berlin concert took place just weeks after Bloody Sunday in Selma, Ala. In 1957, Armstrong had been one of the few black stars to speak out when Gov. Orval Faubus of Arkansas called out the National Guard to block black students from attending Little Rock Central High School. Eight years later, Armstrong spoke out again. Asked for his reaction to the attack on the Selma marchers, he replied that he became “physically ill” watching it on television, and that if he had been marching the police would have “beat me on the mouth.” Then he added, “They would beat Jesus if he was black and marched.”

The East German reporters, hoping to get a similar reaction, peppered him with questions about race relations upon his arrival. But he wouldn’t go there. Although his Iron Curtain tour was not State Department sponsored, one gets the sense that he didn’t want to bad-mouth America while in a communist country, that to do so in the middle of the Cold War would be disloyal somehow. At a news conference a few days before the concert — a clip of which was shown at the screening the other night — he sat grim-faced, smoking a cigarette, testily deflecting questions about how he was treated in the South.

But he did have something to say, and he said it powerfully through his music. In East Berlin he played a song entitled “(What Did I Do to Be So) Black and Blue?” According to Ricky Riccardi, one of Armstrong’s biographers, the song had not been in his repertoire for a decade or more. But 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.