Somewhere in Time: John Barry or Rachmaninoff?

[Rachmaninoff]

I'm listening to Somewhere in Time soundtrack, a solo piano song (5:23). I've heard about Rachmaninoff's Rhapsody on a Theme of Paganini, but I found absolutely no similarities, except by the 18th variation, which is the second part of the Barry's song.

So, John Barry just added the 18th variation as a 2nd part of the song, being original on its 1st part? Or I'm missing something?