Wait until you learn about live beyond 12TET

In short: no you're factually wrong. Human ear can discern smaller pitch changes and there actually music composed on smaller subdivisions than 12

For instance https://en.wikipedia.org/wiki/19_equal_temperament

You can check done pieces on YouTube.

Yes it sounds unusual. Yes it sounds strange. But thats just because you've been conditioned to listen 12 tet all your life.

But saying 12 notes because we can't perceive smaller changes is, again, wrong and there's actual counterexamples of music done with smaller changes

While you are 100% correct a very simple counter example to the op that a lot of people have likely heard in their life is someone tuning a guitar. It would have saved me a lot of time if people couldn't tell the difference. :D

You can test this in the Vienna museum of music. There is a live demonstration with a headphone and with two knobs for the frequency of two separate tones playing together. Also, it visually shows the pitch of those two. If you go below the 12 tone pitch you hear only one tone, near the 12 tone pitch this one tone becomes suddenly to two separate tones.

No. Go look at Ragas in indian music.

“Ragas are precise melody forms. A raga is not a mere scale nor is it a mode. Each Raga has it’s own ascending and descending movement. And those subtle touches and uses of micro tones and stresses on particular notes like this…”

Microtones are less than the difference between two adjacent pitches in western scales and are discernable, even to people like me who have a hard time telling adjacent pitches apart.

In melodic performances that take a `bluesy' approach to pitch, it can absolutely by heard when a note is somewhere in between two equal tempered pitches.

For example, lots of the notes in the vocal of the Beatles `Come Together' are clearly (often very) flat — wonderfully so, subversively so, even, in our pitch-corrected age!

If they sound together, you hear only one beating tone. One after another, you can distinguish them below the 12 tone pitch.

Okay, I get what you are saying. Two simultaneous notes a minor 2nd apart sound like two distinct notes. But you don't have to narrow the gap by much more before it sounds like a single note.

A very small gap gives a subtle chorus effect, a little wider takes one into honky-tonk piano territory, and wider still perhaps more like a bell, but still sounding like one note.

But, as you say this doesn't negate the audibility of microtonal inflections in a melodic line.

However, pitch steps smaller that those of 12tet can still provide new chords. For example, in 24tet the triad with a third half-way between minor and major is a distinct and interesting sound. But yes, in 24tet two consecutive pitches sounded together sounds more like a single note with an interesting timbre.

Yes I do not negate that microtonal has interesting effects. The question was why there a 12 tones in western music. And the answer is that minor 2nd is the smallest interval you can separate when played together. I should have been more precise in my initial comment.

No.

There are systems that have more than 12 notes.

Plenty of instruments hit these "microtones". E.g. string instruments with frets can bend strings, and string instruments without frets can just play those notes.

Genres of music like the blues frequently utilize these microtones.

12TET is just the custom in western music, but we can absolutely discern smaller intervals.

yes, there are more than 12 tones, obviously. But If you play two neighbor microtonal tones together, you hear only one beating.

You can play with a 31/43/53 note keyboard yourself to see that you’re incorrect.

http://terpstrakeyboard.com/web-app/keys.htm

You can not differentiate two microtones playing together at the same time. Unfortunately, I could not test this with your link, because I could only play one after another.

You must not play an instrument because this is completely absurd.

I play the piano for a long time. And I have a clavichord that I tune myself and can tune microtonal to make such tests, which I do.

I can clearly hear different microtone combinations when playing multiple neighbors at the same time on the linked 53 note keyboard.

I'm sure at some point those tones will converge into a single note to human ears, but the fact that a 53-note keyboard exists shows that people can absolutely hear smaller divisions than just the 12 standard notes.

This doesn't ring (pun intended) true:

https://www.sciencedirect.com/topics/medicine-and-dentistry/...