Thank you. It is actually a double fugue with a few extra contrapuntal fillips: the subject of the second section is accompanied at the beginning with an augmented faburden of the first subject (this is “faburden” in the Tudor (Henrician) organists’ sense, wherein the organist derives a new subject by harmonising the original subject in faburden, and then taking the bass of the harmonisation); and the beginning of the third section not only combines the two subjects, but sets them with an augmented inversion of the first subject in the bass. There is also the usual assortment of stretti, and the second section features a recurring countersubject. However…
…if I’ve done my job properly, you shouldn’t notice any of that. I’m not averse to a certain contrapuntal virtuosity, but I prefer that it not detract from the Affekt of the piece, which, in this case, I see as mainly contemplative and melancholy, verging on tragic near the end (hence the accelerando). If someone wants to “Gould” the tempi, I can’t very well stop him/her, but I will get on his/her case if it doesn’t work. 
