A student at the music school where I do clavichord lessons was preparing for a piano degree and was playing the Prelude and Fugue in D major from WTK I. The tempo of the prelude was a bit slow but quite reasonable to my ears, however one of the listeners said that the student should play it faster. (How much faster? I don't know.)
I then looked up more performances on YouTube of this prelude and, to my amazement, most of them are basically at almost double tempo with two notable exceptions: Wim Winters, who tends to play everything much slower because of his "Double Beat" theory (which doesn't make sense to me); and BachScholar who claims to have found a scientific method for determining tempi (I haven't looked into it, but I probably wouldn't say it's accurate either). However, I tend to lean towards Wim's and BachScholar's interpretations, as they speak more musically to me; the others tend to focus on the bass line and almost treat the treble line as ornaments.
I also asked my clavichord teacher about this; he said that Bach probably didn't intend this prelude to be played very fast (although no tempo markings are provided), and he also provided the argument that near the end of it there is a passage of 32ths. (How would you play it at an almost "presto" tempo? Indeed most of the fast performers slow down almost by half there.)
I created a MIDI file of the prelude (the attachment). Its tempo is 90, which is my preferred one. However, I think that it still should be slowed down at the arpeggii and near the end, but I didn't implement that in the MIDI file.
So, the question is: what is your preferred tempo? (You can tweak the provided MIDI file if you want.)
Thank you in advance!
PS: I'm not going to play the prelude yet, but I'm curious about a generic tempo discussion. I thought to talk about the prelude because it has an unusually big statistical range of tempi.