The fugue of this P&F is a triple fugue. It does not only feature three parts, it features three different themes as well. The relation between these three fugues if the theme of the first fugue: it appears in both other fugues as well. As a reminder I first play the theme of the first fugue. Then I pick the performance up where the first fugue ends; you here the closing chord of the first fugue, and immediately the second fugue theme is stated in the pedals. About half way this fugue (at 3.40) the theme of the first fugue is played together with the second fugue theme.
All three parts together, the fugue is really long. Broken down in seperate fugues, I think you'll agree that the quality of the music is outstanding. Played as one whole, I think the fugue is fatuiging for both player and listener. One fugue at a time, however, it is quite a joyfull experience. I enjoyed practicing and playing this fugue very much. I hope some of that enthousiasm sounds through in my performance and hopefully you'll enjoy listening to it. It's not easy to grasp and play, but it's worth all the effort.