Choreographer Joe Gideon (Roy Scheider) ignores the pleas of his friends and family to take better care of his health. He has been a workaholic and chain smoker for many years, and he develops severe heart problems. He realizes he may die soon, and begins to have imaginary conversations with the Angel of Death, Angelique (Jessica Lange).
Gideon dies while having open heart surgery at a hospital. As he is dying on the operating table, he envisions a huge, elaborate musical number in which he bids goodbye to his life and everyone he has ever known. He sings "Bye, Bye Life" (to the tune of the Everly Brothers' "Bye Bye Love"), and concludes this imaginary musical number by walking happily into the embrace of Angelique, who is waiting for him.
As soon as Gideon enters her embrace in his fantasy, we see his dead body being zipped up into a plastic bag, as doctors prepare to send him to the morgue.
Thanks John L!