Vaguely remember as well. I recall a girl doing research on this person on the nth floor of library -- that is somehow connected. This person is simulated in a virtual world, and then realizes he's a simulation when he cannot compose anything new. The realization occurs amidst Greek or Spanish architecture during a sunrise. Same story? But which?
I probe my brain for another clue... I learned the word "hegemony" while reading this book. Googling "hegemony" and "science fiction" eventually gives Hyperion by Dan Simmons. Google is awesome.
But it was the poet Keats that was simulated.
That was 1989. I bet we can think of an older example. A person resurrected but lacking their "essence" is older than AI.
That isn't the story I'm thinking about. In the story the reconstructed person is in a real body, a real mind - he's been mapped onto a living person's brain. Since his style of music is no longer popular, he produces a new symphony in the style of the day, despite knowing it's still a rehash of his previous work. At the end of the performance, everyone applauds... but they're actually applauding the neuroscientists for their work, not the composer for his, and in the end he gets 'erased' so that the test subject can have his mind back. It might be a story from the 50s, since I seem to remember reading it in an anthology of such.
Go see for yourself.
The complete post is quite long and just as good as this quote.