Very Cool! Thanks for posting.
I'm a very amateurish musician, with little formal training, and I am just amazed at the things Bach has done. I assume I'd be even more amazed if I understood it at a deeper level.
I think I've heard that rising tome done differently before, and I recorded one myself once on a little cassette multi-track recorder and a synth. That was a rising tone which faded in volume as it rose, and then another recorde a few seconds later doing the same. As you build up the tracks it sounds like it is always rising.
I didn't analyze the discreet tones there, but I suspect they start with a lot of high harmonics, then bring in more fundamental tone as they rise in the scale (or vice verse). That can 'trick' you to focus on the tone an octave lower or higher.
OK, one of my fave Bach-influenced tunes: