A final performance, product, or accomplishment before someone or some-thing stops creating work or products, as due to death, retirement, closure
etc. From the ancient belief that swans issue a beautiful song-like sound just before they die.
From the 2016 Wish Book Catalog: Celebrate the 15th anniversary of America’s tolerance of the worst people in the world! Great gifts for anyone who fears free expression (from others), and the folks in your life who do nothing but tear down and destroy! Order now: before the right to criticize anything is taken away by the US government, to appease hateful, murderous bigots! Special discount for submissive would-be dissidents and useless virtue-signalers! Rat out your close friends and family online to get the whole set- FREE!