Skua

What I’m taking from this is that if we had invented Western musical notation in 2016 we would undoubtably have used 🅱for everything

As I understand it, yes. The b rotundum and b quadratum. I actually have no idea where the natural sign comes from though, now that I think about it

I really dislike that German system, but for those that want an explanation:

Traditional European music theory evolved towards using sets of seven notes out of twelve in an octave. We eventually labelled those notes A through to G. Originally A was the lowest note available in common notation and we built our instruments accordingly (see the lowest and highest note on most pianos even today), but we then take a particular liking to the scale that starts on C using this system.

Even though this worked really well most of the time, in each seven note scale there was one standard combination that was pretty harsh (the diminished chord, such as the B chord in C major). To get around this, people just kind of accepted that B could be in two different places - the usual position if that sounded better, the flattened one (one twelfth of the octave lower) if that worked better. The system of sharps and flats wasn’t standard yet - nor was the modern staff system at all, for that matter - and it was only really this note that it mattered for most of the time, so the solution was to write the letter B in two different ways depending on which one you meant. There was a round B and a square B.

And then Germany gets really good at making printing presses. This is very useful for spreading copies of musical notation, but it does present a problem: your press probably doesn’t have two ways to write the letter B. So what do you do instead? Use another letter for one of them. H is the eighth letter, and it even looks kinda like the square B anyway, so that becomes the standard practice.

One fun quirk of this is that it permitted Johann Sebastian Bach to write his last name in musical form, which he went on to do in a whole bunch of his compositions

Presumably you downloaded Microsoft Keyboard Layout Creator (MSKLC), which I still had to do to make a custom keyboard layout in 2022. Funnily enough I was also wanting to use AltGr to add diacritics to vowels, because I don’t want to have to go to the backtick key for àèìòù

For what it’s worth, making a custom layout actually is a huge pain in the arse. That’s a pretty niche use case, but there is definitely no reason for it to be as much of a hassle as it is