Hi Tomo and friends!
As Tomo notes in some videos, the irregularity of the B string on the standard tunning complicates learning a bit. For example, if you're learning the shape of the major scale (playing 1 octave), you have to learn 4 different shapes depending on which string you start. [1]
Another example can be found on triads. A triad has 3 inversions. But shape changes depending on the string that you start as well, so to learn all the triad inversions you have to learn 3x4=12 shapes.
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If we were tunning our guitar with the All Fourths Tuning [2] this wouldn't happen. There's only 1 shape for the major scale, and 1 shape for each triad inversion. And I suspect as you start getting into more complex harmony, having a regular fretboard must simplify the understanding of what's going on further.
I've been playing with the All Forths Tunning for ~6 months now and so far the experience has been nothing but impressive. It has helped me a lot to stop thinking about shapes and understand more about what's going on. A lot of things just become easier and made sense. Here is a video of Allan Holdsworth saying that if he started to learn guitar again he would tune it all-fourths [3].
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The question I've been asking myself is "Why isn't this tunning used instead of the standard tunning?"
My hypothesis is that the "easy part" of guitar (open chords and 6 string chords) is indeed a bit more difficult, nonetheless achievable. And that's the reason why it's not used. Nevertheless, once you're beyond the "easy part" I think the benefit is huge.
I would be super interested to know what others or Tomo thinks. Am I missing something?
Thanks!
[1] https://tomovhxtv.vhx.tv/music-theory-i/videos/theory-01-c-major-scale t=14:00
[2] https://en.wikipedia.org/wiki/All_fourths_tuning
[3] https://streamable.com/njyj8 t = 40s