A bellwether is the sheep with the bell, the one the flock follows, and the summer of 1943 turned out to be a bellwether of its own. The heat came early; the war plants had packed the cities with newcomers competing for the same housing and the same jobs; and in June the tension broke in one city after another—the Zoot Suit Riots in Los Angeles in the first week, a riot in Beaumont, Texas, in the middle of the month, and then the worst of them, in Detroit.

Sunday, June 20, was around ninety degrees, and some 100,000 Detroiters, Black and white, went out to Belle Isle, the city's island park in the Detroit River, to get out of the heat. Fights broke out that evening, rumors raced across town overnight, and by Monday mobs were loose in the streets. Roosevelt sent in federal troops that night, eventually some 6,000 of them. When it was over, 34 people were dead—25 of them Black, 17 of those killed by police—hundreds were injured, and about 1,800 had been arrested. The Arsenal of Democracy had spent three days fighting itself.

It's a strange thing to set beside a dance tune. But the bands played on through all of it, and so did the people who came to hear them, and that is what this one is for.