This piece of music is the Etude Op. 10 No. 4 in C# minor by Frederic Chopin. The concept of Etudes or Studies for piano were nothing new, but previously thought of as being exercises for pianists to practice particular techniques. However Chopin took the concept to a whole new level with his Etudes creating pieces which were rewarding to practice and play, and to listen to. All Chopin's Etudes are very difficult to play, but they are fascinating compositions and useful practice for the advanced piano student. In total Chopin wrote 27 Etudes, a set of 12 called Op.10 and another set of 12 called Op.25 and finally a set of 3 etudes - some are a little easier to play than this one, though many are just as difficult. All 27 are available in book form from these links at Sheet Music Plus (US) or The Music Room (UK). The video below illustrates the music with a graphical animation, or you can play the mp3 file and see the sheet music score before downloading.
Here is a video of Chopin's Etude in C#m for piano:
The audio controls below allow you to play the mp3 version of Chopin's Etude in C#m for piano or you can download the MP3 file. You can also download the midi version of Chopin's Etude in C#m for piano or alternatively edit/play the midi file.
The image below is the first page of the sheet music, and here you can download the full sheet music for Chopin's Etude in C#m for piano in PDF format.