CHICAGO — If you can hum a few bars of “Disco Duck,” have I got a show for you. It is the latest episode of the distinguished PBS “American Experience” series, which has over 35 seasons given television viewers award-winning documentaries about usually weighty subjects, as it dips into disco with an entertaining and thought-provoking hourlong trip. One reason is the presence of Chicago and a number of talking Chicagoans in the episode “The War on Disco,” as the city was the principal battleground in this “war,” with Comiskey Park literally exploding on July 12, 1979. Do you remember that night...