Well, ok, I didn't read the whole thing. But I did read the part where you asked your teacher, "Why does an octave have eight notes?"
There is a scientific answer to this question, and although I'm not going to be able to answer it completely accurately, I hope I can give you an idea of where to look for your answer.
Consider a scale starting at a given note. That note is simply shorthand for a frequency, right? Most orchestras tune to middle A = 440hz. A note an "octave" higher is double the frequency (the A above that would be 880hz). I'm not quite sure what it is that makes this note the "same" as the other note, but most everyone would agree that the A-above-middle-A is the same note, just higher in pitch than middle-A.
So there's the idea of "sameness" in notes going up and down the range. Double the frequency => note one "jump" higher (I'm avoiding the term octave because of its implication of an eight-tone scale...odd, isn't it? There's actually twelve.)
Now imagine you're a musician in the dawn of civilization. Consider an incredibly early stringed instrument...one string taught between two endpoints. Tightened to a certain tension, it rings with a specific tone.
If you put your finger RIGHT on the middle of the string, and get it resonate at exactly twice it's standard frequency, you've made the exact same tone, only an "octave" higher.
If you put your finger RIGHT on the third-way point and get the string to resonate (harmonics on a guitar) then the note you ring is not an octave, but the "dominant" of the note described by the un-touched string.
Continue by stringing a second, parallel string to the first, but tune it to the tone achieved by touching the third-point of the first. Let me attempt to diagram this below:
String 1: |--------------------------| Tuned to "C" (just for kicks)
String 2: |--------------------------| Tuned to the "third-of-the-string-harmonic" of C (happens to be "G")
Continue this proccess for a while, adding strings that are the dominant of the string above, and eventually you'll derive a lot of notes. Like these:
Dominant of G is D
Dominant of D is A
Dominant of A is E
Dominant of E is B
Dominant of B is F#
Dominant of F# is Db
Dominant of Db is Ab
Dominant of Ab is Eb
Dominant of Eb is Bb
Dominant of Bb is F
Dominant of F is C (the same note as the one we started with!!!)
So you've just derived every note, and if you use this particular method (tightening strings and using harmonics on the strings) you'll derive all 12 notes in the diatonic scale, and ONLY the 12 notes in the diatonic scale.
There are other harmonics on a string, but it turns out that they correspond almost EXACTLY to one of the 12 notes we derived above.
It's worth noting that I've read about 10-tone scales used in other cultures, but I'm not totally sure how they derived those scales, nor if they're culturally aware of the idea of an octave...as in two notes which are either double or half of the other's frequency sound "the same" in some deeply rooted way.
I hope this provides at least a basis for why there are 12 notes in a diatonic scale, and where they come from. It's not hard to go from there to the idea of an eight-tone scale by way of the melodic minor scale (popular amongst the monks of the 1200's to 1600's), the major scale (it's a mode of the minor scale, but I'm sure it appeared before any of the other modes of the minor scale, I'm just not sure of the musical history), the pentatonic scale, the natural and harmonic minor scales, etc. And it's also true that the 12 notes of the diatonic scale, whatever you choose to call them, are the building blocks of music based at least partially on their tonal relationships, and not solely because we're culturally conditioned to understand them. Notice the difference between western music and indian (dots not feathers) music. Each is describable in the vocabulary of the other...because they're both based on a 12-tone scale which was more-or-less derived independently from the other.
Music is fascinating, and my understanding is rudimentary. But theory is important for many many many reasons. I'm sorry that your teacher couldn't explain why there are 8 notes in an octave, or why there are only 12 tones in a diatonic scale and where they come from. That doesn't mean that those questions don't have answers.
Your personal experiences don't mean diddly in a nation of 300 million people.
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