I'm trying to identify this episode from some 1980's show. This would have been Twilight Zone, Outer Limits, Monsters, Amazing Stories, one of those shows. The plot was something like: a broadway songwriter dies, and the devil appears. The devil explains that he is a huge fan of the protagonist's music. As a kindness, the devil offers, before taking him to hell, to send him back to when he was a young man, no strings attached. The protagonist naturally accepts.
The guy finds himself a teenager at a party. He realizes that he isn't really enjoying himself at the party surrounded by people who are all 40 years younger than his mind. He starts to play the piano, and the shy girl in the corner comes out and starts to sing to the music, and he is astonished to find that she is an amazing singer. They have a great time at the party, the night is ending and the devil shows up. The protagonist casually says that he barely even remembered the shy girl from school, couldn't believe she was so amazing. The devil explains that after the party, alone and sad, she had commit suicide. The protagonist rushes to find her, and talks her into following her dreams as a singer.
The devil shows up and takes the protagonist back home, which is subtly different. He explains that the pep talk worked and the shy girl went on to become a huge broadway hit, was still alive and well, and produced beautiful music. We realize that the devil really sent the protagonist back in time to save the shy girl's life so that she would go on to make music the devil loves to hear. In the end, either the guys turns out to now be alive because of the changes he made, or his good deed somehow wiped the slate clean or messed up the files, something like that. The devil kind of shrugs and smiles, saying that these things happen.