The 18th variation of Sergei Rachmaninoffs Rhapsody on a Theme of Paganini again shot to fame as a result of the movie.
Listen to it here:
http://www.youtube.com/watch?v=59GQbd8CEO4
In the book (Bid Time Return) it’s Mahler’s 9th Symphony.
Ironically, in the fan site, as well as the original story the music mentioned was Mahler, which had no part in the film.
To appreciate Rachmaninoff’s composition, you must hear it performed by a symphony orchestra.