On Brandenburg movement: Does this have anything to do with delicacy taking over from power because delicacy can do more? That is to say, when Bach became aware of the harpsichord, did he notice the increased speed possible with the delicate notes and did that affect the composition?
On Bach's D minor: Since Bach wrote quite a bit of religious music, is it possible that this represents the common mystical experience in which, as meditation-plus-awareness increases, the music (or outside world) is perceived as slowing down and the notes and transitions (various things) become more beautiful? In fact, to even clearly hear each distinct note in a fast movement, one must slow one's might into meditation, as paradoxical as that might seem. Did Bach then have a mystical state of consciousness when listening to music which caused him to become more aware of the notes and patterns, and caused him to hear more beauty in the music, and if so, did that affect his composition?