Right off the bat after skimming this I'm caught up with a detail that you confirm multiple times - that you can tell literally nothing apart given any input over 70 hz. You have had this measured a few times and you definitely say that nothing is coming across above 70 hz.

Yet you are trying to hear all sorts of things that have most all of their information content above 70hz.

The Hatsune Miku music? You're hearing the bass and the kick drums and maybe some subharmonics generated in the reverberation of the higher stuff. But that is a tiny fraction of the music, and, I hate to tell you this, but that computer girl singing is all way, waaay up higher than 70hz. The beautiful sounds you are getting across are the cool synth basses of all that music. It's very modern, punchy music and the bass of that type of electronic music is very different from other classical music so whatever modulation your implants are doing to it from 70 hz down likely sounds very cool compared to a lot of other music, for sure.

But, stop- you're getting nothing by noise and wind sounds with no information differentiation over 70hz because your brain isn't demodulating that information, maybe due to something about how the implant was... implanted... or just your specific condition, who knows, but what you can do is work in the band you have.

You mention not getting human voices because the fundamentals of human voices are more than 2x where your cutoff is.

Have you tried using a program like Audacity - or - Get claude to write a script for you that takes in MP3's of modern music and slows them down 300-400 %. The music will be very slow, but it will shift instruments from higher up (pianos, horns, people's signing) down into the 20-70 hz range, and you will maybe hear patterns that are new. Did no one in the study post-op sit with you and go thru this kind of thing? You have all these external trials listed but most all of it is moot if everything above 70hz is missing and you aren't able to modify the modulator hardware.

Note that the type of rhythms in the bass of the bass synthesizers of that Hatsune Miku tracks are different that the more complex rhythms and melodies played by instruments higher up (like pianos and lead synths). (This is true for most all music genres...) Shifting those higher up things down in frequency, even if that means they play back slower, may give you an different musical experience.

Continuously pegging your implant modulation hardware with frequency content above 70hz attempting to discover something about how it interacts with your brain when you continuously get nothing but broadband noise over 70hz seems like a dead end exercise.

I mean hell, have you tried putting a low pass filter to block out on everything in the music/microphone input above 70hz just to make sure that information isn't somehow overloading the way the implant works with your brain, and maybe just causing confusion.

Lastly it sounds like you could benefit from talking with someone with a real audio / digital signals processing / electrical engineering background that can inspect your hardware directly and make suggestions because educating yourself with just GPT runs might be spinning you in circles.

For instance... you mention things like " The logic of my test apps, which generate the test sounds and move the staircases, was checked with the Lean 4 formal verifier,"

Man... this has nothing to do with needing a 'Lean 4 formal verifier' to check your app or whatever. You need someone to sit with you and your damn hardware and work with some audio input. You need the someone that setup the original implant modular to explain the hardware mapping and filtering options to you and see if you can go back and change how that works, to get more options. You're getting some wildly mixed signals (bad pun) about how all this works, I think.