I think you’re right to point out the technological aspect of this. From my limited understanding, truly precise 12TET needs a fairly precise way of calculating the twelfth root of 2 (this, multiplied by the base frequency, gives you the length of a given half-step). For a while in history, this just was not done, meaning (on the piano, at least) different keys likely had markedly different characters. Some whiffs of this probably survive if you’re reading the tea leaves, since composers of the era would write music to fit the “mood” of the key…

Of course this all falls apart for some traditions, like unaccompanied choral music, where the tuning is much more free…

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