Has anyone heard this song? I love the part where the arpeggios start! :D

At some parts it seems like Bach didn't have a clue what he was doing but that's what a fantasia is all about: putting what you feel like into the song without worrying if it follows a certain form or rule.

Anyway, although the version of this song that I have for solo piano has the key sig of Dm, since the song is chromatic, it doesn't really matter, does it?