This fugue in C minor is from Johann Sebastian Bach's Well Tempered Clavier, also known as the 48 Preludes and Fugues. The fugue is in 3 parts for most of the first page, becoming darker as the 4th part is added in the lowest voice. The Fugue uses all the devices associated with the form, including obvious inversions (where the tune is played upside down) and augmentations (where the tune is played at half speed). The voices pile up towards the end bringing the work to a dramatic close. Bach's Preludes and Fugues come in matched pairs in the same key, and here is the corresponding Prelude No.2 from book 2, also in C minor, and together the prelude and fugue pair are catalogued as BWV 871.
Although there are some easier preludes and fugues in the set, much of Bach's Well-Tempered Clavier is quite challenging to play. However the complete set has for a long time been considered a must for any serious student of piano. Some other preludes and fugues from the set are available on mfiles if you check the Bach page or Classical Sheet Music page. If you have aspirations to be a good classical pianist then we recommend getting the complete Well-Tempered Clavier which comes in two books. Here are links on "sheet music plus" to Book 1 and Book 2 of the Well-Tempered Clavier.
The audio controls below allow you to play the mp3 version of Bach's Fugue No. 2 in C minor from Book 2 or you can download the MP3 file. You can also download the midi version of Bach's Fugue No. 2 in C minor from Book 2 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 Bach's Fugue No.2 from book 2 in PDF format.