Yes, the names are important for "interop" reasons and yes, historically they mattered because the temperament was different and C# was totally different from Db. And yes, not all modern music is based on the 12-note equal temp. But for a beginner, I would advocate avoiding them and thinking in terms of semi-tones as I've described. It's simpler, and it's the way guitars and pianos and DAWs and whatnot work, so it's a good way of thinking for a beginner. I know for sure I didn't appreciate being bombarded with names like "augmented fourth" or "diminished seventh" when "+6“ or "+9" would make more sense in terms of piano keys/frets that beginners usually have in front of them.
> But for a beginner, I would advocate avoiding them and thinking in terms of semi-tones as I've described.
For a total beginner, I might agree. But thinking about the scale degrees (Do, Re, Mi etc.) is also a totally viable approach (even as a starting point), and it's extremely helpful to learn about how the two relate ASAP so you aren't left holding a mess of seemingly-contradictory "theories" in your head!
Historically, they sounded different, so they wouldn't even be acoustically in-tune w/ the same notes. Each would only be in tune with its nearby notes on the "extended" cycle of fifths.
Yes, and it means that songs actually sound different when played in different keys. It's not just a shift up or down, the intervals within the song shift, if only slightly.
Indeed "slightly different", as opposed to "totally different", which they are not.
And apparently the human ear can be train to ignore this slight difference (which everybody does because we are used to 12-TET). And this, for me, kind of throws the whole "simple integer fraction ratio == pleasing harmony" a bit into question. It's probably not wrong, but there's definitely more to it. But it's hard to explore, because you need the exposure to get used to the new microtonals if you want to experiment with it. Definitely very hard to test scientifically because it depends so much on a particular person's musical background and education.