This piano music is the Prelude in G minor Op. 23 No. 5 by Sergei Rachmaninoff. Like many of the composer's preludes this is a difficult piece to play, but rewarding to practice for the advanced music student. The outer sections are march-like in character with a flowing middle section. The video below shows the music being played in "piano roll" format, and below the video you can play the mp3 file or view the sheet music. You can download this sheet music in PDF format, and the corresponding midi and mp3 files using the links in the left-hand menu.
Like the composer Chopin (and Bach before that) Rachmaninoff wrote a total of 24 preludes, one in each key both major and minor. However unlike other composers, Rachmaninoff didn't appear to set out initially to create 24 in different keys as there seems to be no particular order to their composition or publication.