I'm not sure about the target audience. For example, I looked at the Pitch poster (notation-pitch.pdf), and it seems to target people starting out on the piano. Nothing wrong with that, but people starting on instruments that don't have pre-programmed pitches (violin, cello, trombone, ...) Probably want to know there's a difference between fi c-sharp and d-flat.
Also, there's a cultural divide in how you read notes (movable-do versus fixed-do) and I'm not sure what you want to do with that.
Music theory is a cultural artifact encompassing centuries of development. It can be challenging to newcomers, but just like in complex software systems, there are often good reasons why things are the way they are.
... and even more often, historical artifacts which built up for no good reasons, but which aren't worth fixing due to everyone knowing it this way.
Music notation is a mess.
I'm not proposing changing it (that would make no sense -- it's good enough), but it's not worth treating as somehow right. Centuries of unplanned historical evolution don't necessarily result in something rational.
To go with your analogy: it's like the legacy software system written in Fortran which runs on VMS. There's a ton of institutional knowledge and good ideas, but a ton of cruft too.
The nice part is that, in fact, you can ignore most of it unless you are explicitly aiming to reproduce and capture elements of older works. If you are composing new work, you never really have to learn theory, but a few of the most popular frameworks help things along(e.g. composing to familiar meter, motif and chord structure does a ton to fill in gaps) and as a professional getting some familiarity with repertoire, if not necessarily its underlying theory, is expected. But once you have some distinct patterns to play around with, the music is already nearly there, and it's just a case of elaboration and refinement in some direction.
In that sense it's much more forgiving than software. Software becomes indecipherable almost as soon as nobody is looking at it and its structures are in some sense necessary for a purpose. It's not as amenable to pragmatic solutions although often, more of them are possible than we recognize.
Well, I think there are more basic notational issues too, which you can't ignore; they affect everyone. For example, the way that sharps and flats work makes no rational sense, except in the context of history of instruments and scales.
A lot of the notation of timing is cumbersome. Why the large number of wonky-looking symbols? Compare to how a lot of composition software shows timing with how long a position notes take up horizontally (music notation predates the concept of Cartesian coordinates!). It's a lot easier to work with, in all respects.
All this stuff builds up to about an unnecessary 3-month learning curve for kids learning music notation.
Is it worth changing a whole industry -- where everyone already knows the notation and there are countless works in notation -- to save all kids three months? Maybe, but probably not. That's the legacy system problem.
The nice thing -- compared to software systems -- is that none of this stuff is really all that complex.
Because music theory doesn't know how numbers work. The interval of A(440Hz) to A(440Hz) is "1" in music theory even though it's 0 in literally every other context ever in the history of everything. I mean, if they're going to use a bunch of mathematical terminology, the least they can do is count right.
It's not a "1", it's a "prime" and the root of that word is an ordinal (whence "first") not a cardinal. There is no zero'th ordinal. There is just "none", which implies that A to A is simply not an interval.
most of it was built before people understood why/how some things work. Take for example scales. In the beginning, you learn that over a C7 chord, you can use the mixolydian scale. Fine. But then you discover that the minor third (e-flat) can work too, and the major 7th can work as well (fe bebop scale). Then you discover that the others can work too (yes even the minor 2nd) and depends on other things like strong-beat/weak beat and what you're resolving to. Classical music theory has no framework to explain all the things that can work. (The reason why all of the above works is still better explained by physics)
I think that's a mischaracterization, because it assumes that it was ever designed. At each point in time it was assembled from the notation conventions familiar from the previous generation of music to record the current generation. As you go back in time you find a nice, continuous progression back to about the 9th century.
I'm not sure about the target audience. For example, I looked at the Pitch poster (notation-pitch.pdf), and it seems to target people starting out on the piano. Nothing wrong with that, but people starting on instruments that don't have pre-programmed pitches (violin, cello, trombone, ...) Probably want to know there's a difference between fi c-sharp and d-flat.
Also, there's a cultural divide in how you read notes (movable-do versus fixed-do) and I'm not sure what you want to do with that.
Music theory is a mess.