I have many questions, but all related to the necessity (if any) of the diatonic scale and the consequences of this choice. First: what are the reasons behind the choice of the Western Music diatonic scale with its definite pattern of tones and half-tones?
Who made this choice and why? Was this choice a limiting one? Does it rule out a wealth of non-diatonic music? Were they some important composers and instrument builders who used different scales or just wrote music out of the chromatic scale?
What if the music I have in my mind is non-diatonic? I know I can constraint it into a diatonic melody, but it is not the same music and can be more or less beautiful than the original, depending on the tune. It looks to me I can still harmonize it by combining notes. Yes, the number of combinations mathematically explodes, but the constraints of (ease of) playability on a certain instrument reduces all possible choices quite a bit. And of course it is up to the artist to choose for the better.
Are there other music theories not based on the diatonic scale? Why some out-of-scale chords sometimes embellish a melody better than in-scale chords? Does this make music theory arbitrary and useless because it is based on a too restrictive premise like the diatonic scale?