I'm not too surprised by this. I've had awful relative pitch all my life, and just recently started ear training. I've also for fun read a bit about how absolute pitch develops in young children.[1]

Bit by bit, I'm realising how much of what's taken for granted by practitioners of Western music is in fact learned.

As a concrete example: ever since I was a child, I've heard people speak of major and minor triads as sounding happy or sad. That seems like something that's just obvious to a lot of people. It's never been obvious to me, and it lead me to think I was (at least partially) tone deaf; if I can't even hear something that is (evidently) that obvious to so many people, how can I ever get better at truly listening to music?

Now that I've started ear training, I'm beginning to mentally associate particular sounds with these chord qualities[2] to the point of actually being able to identify them better than a flipped coin would. (Which is a huge milestone for me!)

But it's taken a lot of practise. And I still don't hear them as "happy" and "sad". If I try to listen for "happy" and "sad" chords, I go back to mischaracterising these chord qualities just as much as before. I've simply never learned that association, for whatever reason.

----

It goes on and on: I played a lot of piano (from sheet music) when I was young, and practised the C major scale up and down and up and down, resulting in the interval from the tonic to the major second being etched into my brain very strongly. And I suspect this is what has made it surprisingly hard for me to internally hear a half-step from the tonic. To my brain (before I started ear training), the minimal possible step from the tonic was to the major second. There just weren't any sounds my brain could produce in between.

Learned. With plenty of ear training, I'm now in addition learning to be able to reproduce a minor second too.

Even more speculatively, I've noticed there are some specific half-step intervals I hear as whole steps. These are from E to F, and from B to C. These are half steps, but they are outliers in how often I attempt to classify them as whole steps. I suspect this is because of said C major scale practise: somewhere in the back of my mind, I might associate these tones (in the absolute pitch sense) with steps of the C major scale and therefore think of them as whole steps. I don't have absolute pitch in any useful sense, but it wouldn't surprise me if my brain, somewhere in a back compartment somewhere, has retained the sound of these tones and associated them with adjacent steps in the scale I practised so much.

----

Circling back to octaves: Yes, there are physical bases for considering octaves as a special case of some sort, namely that if you strip out the base resonance frequency of one tone on a string or wind instrument, what you're left with are its overtones, which also makes up its octave's frequencies.

But the fact that this relationship is something that makes these tones sound "the same" might very well be learned. The fact that this level of consonance is even desirable might very well be learned. I can picture cultures in which that level of consonance is considered uninteresting, hollow, and weak. Why would one deliberately care to seek something like that?

----

[1]: By listening a lot to music that extensively and unpredictably uses the 12 tones of Western music in A440 equal temperament tuning, children can learn to recognise these specific 12 tones in that tuning – but it won't help with any other frequencies!

[2]: I now hear major triads as a combination of hollow and triumphant, and minor triads as fuller and more epic. Some parts of it make sense, others do not.