It is given with sound of organ, but it is not playable on this instrument, and probably at all. It is given in 4 separate staves (for 4 voices of the fugato).
http://www.box.net/shared/4q79dkybx7 - mid file
http://www.box.net/shared/qvvfjlu8xn - pdf file
(I gave also PDF with colorful subjects, to show some concepts in this work more easily.)
Enjoy!