I read this story many years ago, probably as a short story in a science fiction magazine in the 80's.
It was a fantastic story that took place in the near future on a colony on Mars where a disease had taken over Earth and moved onto killing the remaining colonists of Mars.
The main character goes to something that was described like a holodeck that repeatedly produced a hologram about a man playing a piano in his ship.
Later he meets a super-intelligent being or beings that offers him the chance to escape his mortal coil and experience the universe in their perception of time. He transcends his body and becomes a star and witnesses cosmic time and the rise and fall of galaxies, cosmic timescales and the history of other beings.
It wasn't written by Isaac Asimov but I do think it was in one of his publications.