In 1971, not long before his death at age 69, the great Louis Armstrong — “Pops,” to his friends — played at the National Press Club in Washington. It was his last public trumpet performance, and it was recorded by CBS. A few hundred copies were made — then it was pretty much forgotten. Now the recording has been re-discovered and it’s being released. CBS News cultural correspondent and jazz great Wynton Marsalis gave it a listen.